i can't remember if this was an issue before 3.0, but when putting a model together in 3.0 i noticed that it becomes really hard to place items. my model parts are built with a lot of transparent space around them (everything is saved from the same large canvas) and it seemed like there was an issue with those hitboxes overlapping. here's a quick rundown of what kept happening:
1. i would pick up a piece -- for example, SILENT MOUTH on layer 3 -- try to move it.
2. EXACTLY when i let go of my mouse click, i would instead get the notification in the top right that a different piece had been moved -- i.e. "moved GLASSES" or "moved UPPER HAIR," from different layers, and that piece would become selected.
3. then, when clicking away from honk to test, the piece i was trying to move would LOOK like it was in the right place, but the moment i started talking (activating the mouth movements), it would snap back to where it was before. this did also happen even before i had a mouth sprite set, voice activation just seems like the precise thing that would kind of "knock" pieces back to where they were before.
you can see it happening a lot throughout this entire video, but for quick reference there's some repeated examples at about the 31 minute mark, and then again at around 38 mins: https://www.twitch.tv/videos/1495247409
i managed to get things in place anyway by grabbing the very very edges of the piece hitboxes and scooting them into place bit by bit (this is why me + my twitch chat ended up thinking maybe it was an overlap issue), so while i haven't had time to test it yet, i'm sure a workaround for now is just to resave all my pngs with the excess transparency cropped away. but because the selection switch seems to happen when i let go of mouse clicks, i wonder if there's a way to tweak things so that once you select a piece and drag it, another piece won't be selected until you do a new click, or something similar? especially since some pieces will always overlap no matter what, and it makes adjustments pretty tough.