I wish I had a better description for the problem, but all I know is that my datapack doesn't work as consistently as it did in prior versions of CPM. When loading into the world some animations may randomly fail to be triggered, but there's no indicator to my knowledge, even in the log files. Whether or not an animation will work or not also changes after reloading the world.

I don't know if I'm playing too many animations at once, if I'm playing animations too fast, or if there's some other problem going on.

For reference when everything is working my testing model will show the armor type being worn, the armor trim, what the armor trim is made of, whether or not it is enchanted, among other things. The datapack will also automatically set the animations to frame 0 when not in use. But the bug may cause 1 or more of these functions to fail.

I have a few screenshots to illustrate the problem in multiple Minecraft versions. (Look to the right of the screen to see the armor indicators. Sometimes they reflect the armor, sometimes not, but if I quit to the main menu and reopen the world, it will randomly start or stop working.)