I tested versions 3.0.49/3.0.50 and 3.1.31/3.1.32 and in both, when transitioning between controllers, a frame of the default pose will appear in between.

This persists between all the versions that I tested in multiple projects. Also, looping animations will either not stop or not start at all. I've tested the example car model and the issue is present, so I know it is neither my code nor models that are causing this. (only on versions 3.0.50 and 3.1.32)

Reverting back down to 3.1.30 or 3.0.48 seems to fix everything.

https://imgur.com/9hRQKTe.mp4

This was recorded in a new, completely clean 1.19.2 project with version 3.1.32

Same issues and more https://imgur.com/NEkpcuz.mp4

3.1.29 breaks model parts
3.1.31 breaks animation controllers (laggy transition)
3.1.32 (not shown in the video) broke all of my looping animations even after updating to the new methods

Actually, in 3.1.32 my poor model was even more broken with some parts not even being part of the body anymore...

This is fixed in dev with more fixes coming, no ETA on release.