My armature deformations inexplicably 'pop', without any shape keys or other modifiers. What's going on? When I rotate my armature in certain positions, the mesh lurches outward into strange positions.  I've already checked out my weight painting, and there's no other modifiers causing any issues -- what's going on?

What could be?

Modifier actived: armature//corrective smooth



Here a picture from behind



Here the file:
When in doubt, check out the various settings in Properties >> Bone Settings >> Deform Tab.  If there's more than one segment under 'Curved Bones', try dialing it down to 1.  While sub-dividing curved bones can lead to higher-resolution deformations, they are also problematic, and hard to trouble-shoot.  If you really want to have those high-resolution deformations, try selecting 'Multiply' on the deformation settings for nearby, connected bones.  Also do lots of testing before animating.