I love my Casio for exercising and hiking and the like.

Casios are, by and large, disposable items. They are not meant to be serviced. They are meant to be replaced. And there are countless stories of Casio putting a LOT of threadlock on those screws for that reason. For some you can get aroudn that to swap a battery or replace a lug but the "preferred" method is to send it to Casio and, if it is under warranty, they basically just send you a new one instead.

And the higher end Casios have twisting backplates that ARE meant to be repaired/maintained have the same twisting backplates as the rest.