I can't imagine the drive slowing down being the issue, but then again I also never saw this bug nor did anyone report it before. If you have access to a different PC or a different drive, maybe you can try the game there, and let me know if the problem still appears.
Viewing post in Caliross, The Shapeshifter's Legacy comments
Glad to know it seems to be working fine now, at least. Since the animation basically just switches quickly between the various frames and then cycles back at the end, perhaps a faulty drive can't keep up with having to access a different file every frame, and that causes timing issues or something (perhaps because of how RPG Maker handles images). I am just speculating, however. This is an old engine, and it doesn't use the GPU much (if at all), making it harder to compare with modern games.