This is what happens when I reopen epics multiple times - all items just juming around like crazy.
First feedback from support was (2 months ago):
"We discussed this with our internal team and indeed this is the expected behavior because we don't have an ordering method for Epics."
Maybe if the topic gets some more attention it will be resolved.
It might be more efficient to use the feedback button on the epics page itself. I know the epics team reads the feedback items there and actively resolves issues like these.