SGM 5.1.1, iPhone 13 running iOS 15.6.1
I'm also seeing this issue -- it mostly (only?) seems to affect unconscious Big Bands, who of course is the most disruptive character this could happen with.
Edit: Now that I'm watching for it more closely, it seems to affect most/all characters and is triggered by the point characters changing display layers while overlapping a body, e.g. when I block the AI's attack, then counterattack into their block.