If a tank is rotated with wasdqe the deformation arrow don't update.
The screenshot doesn't show this but it's easy to replicate. Just place a tank and press w multiple times.
EDIT: I've changed the name from "Tank deformation not updating" to "Rotation values not updated" because I've found another error directly related.
Place a part, enter rotation menu and rotate it with wasdqe. Rotation values won't change. This could be the cause of deformation arrows not rotating with the part.