When attempting to load an animation on a character using :LoadAnimation(), if the animation fails to load for any reason (network error, invalid ID, insufficient permissions, etc), the unloaded animation will still take up a slot in the Animator’s 64-track queue and permanently persist even if attempted to be manually removed. This will eventually lead to other animations (including the default movement animations) refusing to load because the animation queue will be filled with broken animations that never get (and can’t be) cleaned up.
Rig type does not matter; this issue occurs both in R6 and R15. This bug is also not studio-exclusive and does occur in live games
A simple reproduction place can be found here:
animation track queue bug.rbxl (90.0 KB)
Within the place, the first two buttons play 1 and 5 broken animations at a time respectively, and the button on the right attempts to stop and destroy all currently playing animation tracks (however, as described, the broken animations do not get cleared). The below image is the list of playing animation tracks directly after pressing this button.
Expected behavior
The expected behavior should be that animations that fail to load do not permanently take up a slot in the playing animation queue, as they do not play. Ideally they should not take up a slot at all