Why does loading the editor mark app for update?

[artemzheg]

haven’t seen this message popping for no reason for a while.
not long ago we’ve tried to figure out what can be the reason:

What triggers the refresh bar to show ("We just updated this page" banner)

The grey bar “We just updated this page. Please refresh the page to get the latest version. You will not be able to use the app until you refresh.” that shows at the top after you make an edit to your design for instance, seems to appear unexpectedly. Is there an comprehensive list of all the types of changes that would trigger it to show? I haven’t been able to find documentation on the topic.

the reason is...

…still unclear