These are very minor and aren't exactly "errors" the skins are laid out exactly like pandemic wanted them. The models map the skin over the body using the same areas multiple times. This part of the skin is located on the colored part of the backpack.
I think I may need to figure out a way to re-map these Battle Droid models. Similar to the way Icemember has re-mapped his clone skins. They no longer need to by symmetrical.