When the relationModel is updated (e.g. a new row is added or removed), the internal relation cache needs a refresh to reflect those changes. Pick-to: 6.8 Fixes: QTBUG-128434 Change-Id: Ie388c01d545564ad7b1424d70267166ac1e4bfd6 Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>