Confusing duplicities in reviews

In reviews, it happens that there are duplicate files present. It does not behave consistently, it occurs even if there is no merge commit selected. Yet I do not understand the purpose of it even if there was a merge commit since most of the time the diffs of the files are almost completely the same.

Please see [UP-10054](https://youtrack.jetbrains.com/issue/UP-10054)

My team hates it so much that we decided to downgrade and wait if it gets fixed.
Could you please point me to the latest version which did not have this _feature_. Am I even able to downgrade?
Are we going to lose the backups?