After leaving the Unity interface to work in another program and returning,
Unity shows the assets import dialog even though nothing has changed.
This worked this way in 2.5 as well, I’ve just never asked.
It usually only happens once more than the original asset import.
Do you mean the import dialog shows indefinitely and stops you from working, or does it just show briefly and then disappear again?
It’s fairly brief, maybe 5-10 seconds, importing the last model that was updated.