Help?? Armature Moves in Pose Mode (even when pose reset & translations cleared)

I have run into a problem in Blender that I simply can’t seem to figure out… :no:

I have an armature (of a snake-like monster) that seems to move significantly whenever placed in pose/object mode (vs. edit mode). I did some searching and found the two solutions often mentioned were 1) to put the armature in the reset position 2) select all bones and punch in ALT+R, ALT+S, and ALT+G to clear the rotation, scale, and location of each bone.

I have done both of these things, but try as I might, my armature still moves a significant amount when toggled between edit mode and pose mode (or edit mode and object mode for that matter).

I proceeded to ‘save as’ and then delete everything from the scene including the geometry the armature was supposed to move. I also removed all the constraints on the bones in pose mode.

Nothing has worked, so I bring this to the community completely stumped. I have attached the file. If anyone has any thoughts or suggestions, I would be VERY grateful to hear some other points of view.

Snake Monster v39_TESTFILE.blend (1.13 MB)

Many thanks in advance for your time!

Kind Regards,