diff --git a/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike-parallel.result b/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike-parallel.result
new file mode 100644
index 00000000000..d5b6c1c75a2
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike-parallel.result
@@ -0,0 +1,59 @@
+include/master-slave.inc
+[connection master]
+connection slave;
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_USE_GTID=NO;
+SET @@GLOBAL.slave_parallel_threads= 1;
+include/start_slave.inc
+# Future events must be logged at least 2 seconds after
+# the slave starts
+connection master;
+# Write events to ensure slave will be consistent with master
+create table t1 (a int);
+connection slave;
+# Enable breakpoints
+SET @save_dbug= @@GLOBAL.debug_dbug;
+SET @@GLOBAL.debug_dbug=
+"+d,pause_sql_thread_on_fde,negate_clock_diff_with_master";
+connection master;
+# Flush logs on master forces slave to generate a Format description
+# event in its relay log
+flush logs;
+connection slave;
+# On the next FDE, the slave should have the master CREATE/INSERT events
+SET DEBUG_SYNC='now WAIT_FOR paused_on_fde';
+# The relay log FDE has been processed - here we check to ensure it was
+# not considered in Seconds_Behind_Master calculation
+Seconds_Behind_Master = '2'
+# Resume slave SQL (worker) thread
+SET @@global.debug_dbug="-d,pause_sql_thread_on_fde";
+SET DEBUG_SYNC='now SIGNAL sql_thread_continue';
+#
+# MDEV-29639
+# When receiving an event after the SQL Thread idles,
+# Seconds_Behind_Master should not update before it updates
+# last_master_timestamp
+connection slave;
+include/stop_slave.inc
+set @@global.debug_dbug="+d,pause_sql_thread_on_next_event";
+include/start_slave.inc
+connection master;
+insert into t1 values(2);
+include/save_master_gtid.inc
+connection slave;
+set debug_sync='now wait_for paused_on_event';
+connection master;
+# Sleeping 1s to create a visible SBM gap between events
+insert into t1 values(3);
+include/save_master_gtid.inc
+connection slave;
+set debug_sync='now wait_for paused_on_event';
+include/stop_slave.inc
+set debug_sync='RESET';
+SET @@global.debug_dbug=$save_dbug;
+SET @@GLOBAL.slave_parallel_threads= DEFAULT;
+include/start_slave.inc
+include/sync_with_master_gtid.inc
+connection master;
+DROP TABLE t1;
+include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike.result b/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike.result
index c208ee2efad..93a1d069745 100644
--- a/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike.result
+++ b/mysql-test/suite/rpl/r/rpl_seconds_behind_master_spike.result
@@ -4,35 +4,29 @@ connection slave;
 include/stop_slave.inc
 CHANGE MASTER TO MASTER_USE_GTID=NO;
 include/start_slave.inc
-include/stop_slave.inc
-SET @save_dbug= @@GLOBAL.debug_dbug;
-SET @@global.debug_dbug="+d,pause_sql_thread_on_relay_fde_after_trans";
-SET @@global.debug_dbug="+d,negate_clock_diff_with_master";
-include/start_slave.inc
 # Future events must be logged at least 2 seconds after
 # the slave starts
 connection master;
 # Write events to ensure slave will be consistent with master
 create table t1 (a int);
-insert into t1 values (1);
+connection slave;
+# Enable breakpoints
+SET @save_dbug= @@GLOBAL.debug_dbug;
+SET @@GLOBAL.debug_dbug=
+"+d,pause_sql_thread_on_fde,negate_clock_diff_with_master";
+connection master;
 # Flush logs on master forces slave to generate a Format description
 # event in its relay log
 flush logs;
 connection slave;
 # On the next FDE, the slave should have the master CREATE/INSERT events
 SET DEBUG_SYNC='now WAIT_FOR paused_on_fde';
-select count(*)=1 from t1;
-count(*)=1
-1
 # The relay log FDE has been processed - here we check to ensure it was
 # not considered in Seconds_Behind_Master calculation
-connection slave1;
-# Safely resume slave SQL thread
-# Prove SQL thread is in state "debug sync point: now"
+Seconds_Behind_Master = '0'
+# Resume slave SQL (worker) thread
 SET @@global.debug_dbug="-d,pause_sql_thread_on_fde";
 SET DEBUG_SYNC='now SIGNAL sql_thread_continue';
-# Wait for SQL thread to continue into normal execution
-SET DEBUG_SYNC='RESET';
 #
 # MDEV-29639
 # When receiving an event after the SQL Thread idles,
diff --git a/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike-parallel.test b/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike-parallel.test
new file mode 100644
index 00000000000..7d29ae61d2a
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike-parallel.test
@@ -0,0 +1,2 @@
+--let $slave_parallel_threads= 1
+--source ./rpl_seconds_behind_master_spike.test
diff --git a/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike.test b/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike.test
index a80dedb7383..fead02da051 100644
--- a/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike.test
+++ b/mysql-test/suite/rpl/t/rpl_seconds_behind_master_spike.test
@@ -18,6 +18,8 @@
 #
 # References:
 #   MDEV-16091: Seconds_Behind_Master spikes to millions of seconds
+#   MDEV-25999: Unrealistic "Seconds behind master" value
+#   MDEV-36840: Seconds_Behind_Master Spike at Log Rotation on Parallel Replica
 #
 --source include/have_debug.inc
 --source include/have_debug_sync.inc
@@ -29,12 +31,10 @@
 # Using_Gtid needs to start as NO before updating debug_dbug
 --source include/stop_slave.inc
 CHANGE MASTER TO MASTER_USE_GTID=NO;
---source include/start_slave.inc
-
---source include/stop_slave.inc
-SET @save_dbug= @@GLOBAL.debug_dbug;
-SET @@global.debug_dbug="+d,pause_sql_thread_on_relay_fde_after_trans";
-SET @@global.debug_dbug="+d,negate_clock_diff_with_master";
+if ($slave_parallel_threads)
+{
+  --eval SET @@GLOBAL.slave_parallel_threads= $slave_parallel_threads
+}
 --source include/start_slave.inc
 
 --let $sleep_time=2
@@ -45,56 +45,37 @@ SET @@global.debug_dbug="+d,negate_clock_diff_with_master";
 --connection master
 --echo # Write events to ensure slave will be consistent with master
 create table t1 (a int);
-insert into t1 values (1);
---let $t_master_events_logged= `SELECT UNIX_TIMESTAMP()`
+--sync_slave_with_master
 
+--echo # Enable breakpoints
+SET @save_dbug= @@GLOBAL.debug_dbug;
+SET @@GLOBAL.debug_dbug=
+  "+d,pause_sql_thread_on_fde,negate_clock_diff_with_master";
+
+--connection master
 --echo # Flush logs on master forces slave to generate a Format description
 --echo # event in its relay log
 flush logs;
 
 --connection slave
 --echo # On the next FDE, the slave should have the master CREATE/INSERT events
+--sleep $sleep_time
 SET DEBUG_SYNC='now WAIT_FOR paused_on_fde';
-select count(*)=1 from t1;
 
 --echo # The relay log FDE has been processed - here we check to ensure it was
 --echo # not considered in Seconds_Behind_Master calculation
---connection slave1
-let $sbm= query_get_value(SHOW SLAVE STATUS, Seconds_Behind_Master, 1);
---let $t_now= `SELECT UNIX_TIMESTAMP()`
-
-# Ensure Seconds_Behind_Master does not point beyond when we have proven the
-# events we have proven to have executed. The extra second is needed as a
-# buffer because the recorded times are not exact with when the events were
-# recorded on the master.
-if(`select $sbm > $t_now - $t_master_events_logged + 1`)
-{
-    die "A relay log event was incorrectly used to set Seconds_Behind_Master";
-}
-
---echo # Safely resume slave SQL thread
-
---let $dbug_wait_state="debug sync point: now"
---echo # Prove SQL thread is in state $dbug_wait_state
---let $wait_condition= SELECT STATE=$dbug_wait_state from information_schema.PROCESSLIST where COMMAND="Slave_SQL"
---source include/wait_condition.inc
+# `Seconds_Behind_Master` must remains 0.
+# * MDEV-16091:
+#   It should not point at the FDE's `start_slave.inc` timestamp.
+# * MDEV-25999 & MDEV-36840:
+#   It should not point at all in a new stream, for FDEs are not content.
+--let $status_items= Seconds_Behind_Master
+--source include/show_slave_status.inc
 
+--echo # Resume slave SQL (worker) thread
 SET @@global.debug_dbug="-d,pause_sql_thread_on_fde";
 SET DEBUG_SYNC='now SIGNAL sql_thread_continue';
 
-# We have to wait for the SQL thread to acknowledge the sql_thread_continue
-# signal. Otherwise the below RESET command can overwrite the signal before
-# the SQL thread is notified to proceed, causing it to "permanently" become
-# stuck awaiting the signal (until timeout is reached).
-
---echo # Wait for SQL thread to continue into normal execution
---let $wait_condition= SELECT STATE!= $dbug_wait_state from information_schema.PROCESSLIST where COMMAND="Slave_SQL"
---source include/wait_condition.inc
-
-# Reset last sql_thread_continue signal
-SET DEBUG_SYNC='RESET';
-
-
 --echo #
 --echo # MDEV-29639
 --echo # When receiving an event after the SQL Thread idles,
@@ -178,6 +159,10 @@ while (!$caught_up)
 --source include/stop_slave.inc
 set debug_sync='RESET';
 SET @@global.debug_dbug=$save_dbug;
+if ($slave_parallel_threads)
+{
+  SET @@GLOBAL.slave_parallel_threads= DEFAULT;
+}
 --source include/start_slave.inc
 --source include/sync_with_master_gtid.inc
 
diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index 70b80e8884f..34af0b4d028 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -104,6 +104,14 @@ handle_queued_pos_update(THD *thd, rpl_parallel_thread::queued_event *qev)
       (e->force_abort && !rli->stop_for_until))
     return;
 
+  #ifdef ENABLED_DEBUG_SYNC
+    DBUG_EXECUTE_IF("pause_sql_thread_on_fde",
+      DBUG_ASSERT(!debug_sync_set_action(thd, STRING_WITH_LEN(
+        "now SIGNAL paused_on_fde WAIT_FOR sql_thread_continue"
+      )));
+    );
+  #endif
+
   mysql_mutex_lock(&rli->data_lock);
   cmp= compare_log_name(rli->group_relay_log_name, qev->event_relay_log_name);
   if (cmp < 0)
diff --git a/sql/slave.cc b/sql/slave.cc
index c08a6f2b84b..b092dbe38bb 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -4511,15 +4511,6 @@ static int exec_relay_log_event(THD* thd, Relay_log_info* rli,
     {
       Gtid_log_event *gev= static_cast<Gtid_log_event *>(ev);
 
-#ifdef ENABLED_DEBUG_SYNC
-    DBUG_EXECUTE_IF(
-        "pause_sql_thread_on_relay_fde_after_trans",
-        {
-          DBUG_SET("-d,pause_sql_thread_on_relay_fde_after_trans");
-          DBUG_SET("+d,pause_sql_thread_on_next_relay_fde");
-        });
-#endif
-
       /*
         For GTID, allocate a new sub_id for the given domain_id.
         The sub_id must be allocated in increasing order of binlog order.
@@ -4671,16 +4662,13 @@ static int exec_relay_log_event(THD* thd, Relay_log_info* rli,
     wsrep_after_statement(thd);
 #endif /* WITH_WSREP */
 #ifdef ENABLED_DEBUG_SYNC
-    DBUG_EXECUTE_IF(
-        "pause_sql_thread_on_next_relay_fde",
-        if (ev && typ == FORMAT_DESCRIPTION_EVENT &&
-            ((Format_description_log_event *) ev)->is_relay_log_event()) {
-          DBUG_ASSERT(!debug_sync_set_action(
-              thd,
-              STRING_WITH_LEN(
-                  "now SIGNAL paused_on_fde WAIT_FOR sql_thread_continue")));
-          DBUG_SET("-d,pause_sql_thread_on_next_relay_fde");
-        });
+    // Note: Parallel Replication does not hit this point.
+    DBUG_EXECUTE_IF("pause_sql_thread_on_fde",
+      if (typ == FORMAT_DESCRIPTION_EVENT)
+        DBUG_ASSERT(!debug_sync_set_action(thd, STRING_WITH_LEN(
+          "now SIGNAL paused_on_fde WAIT_FOR sql_thread_continue"
+        )));
+    );
 #endif
 
     DBUG_RETURN(exec_res);