I downloaded an earlier version (4.0.0.0, to be exact) and saw that I wasn't crazy... The animation looks fine there... (please ignore the fact that the GIFs are slightly offsync, that's not important)
Just out of curiosity I decided to slow down both GIFs and found out why does the animation feel a bit wrong. Movement and animation loop are indeed just slightly offsync! The loop delay is just a frame behind the step delay, compared to the older versions where both were perfectly in sync.
Then I started searching through different versions between 4.0.0.0 and 4.4.0.5 to find which of these initiated that little misbehavior and found out it was 4.3.7.0. Judging by it's changelog... Yeah, it was one of such versions where there were a few different fixes and changes regarding animations, including pausable global anims and fixes on anim's initiation...
- added pausing global animations on playfield if game engine is paused
- fixed setting global animation sync frame when started with “.init_event”
- fixed one-frame delay when global animations leave “init” state
I think the last part is the culprit here.