Graph Editor Handles are Changing Without My Touching Them

This has happened multiple times now and I cannot find any information on the subject. I’ll spend hours, days, splining out an animation only to at some point have the movement become stilted. I look at the graph editor and, lo and behold, all my handles are pulled out, leading to bad movement.

This is infuriating and seemingly unusable, and I want to know if anyone has encountered something similar. I’m not going to share the Blend because it’s pornographic, but I’ve included a picture of what happens, and would be happy to give any more information. This was splined out perfectly and now all my curves on every bone are pulled out. Am I missing something?