Unexpected bone movement when switching between animations.

Hello!
When I switch between one animation and another in the action list, sometimes, some bones are moved. Then, if I switch to another animation from the list and go back to the previous one, depending on the animation I switch from, the one that looked wrong fixes itself, and so on.

It’s not a visual issue because when I export, the animations that look “wrong” also export incorrectly.

I had thought that maybe there were empty keyframes between one animation and another, and Blender was “overlaying” the information from one bone to another, but it seems that’s not the case either?

Does anyone know what’s happening or how I can fix it? Thank you.