Ground down/bashed in lug corner aside, just unscrew the case back, tighten that screw up, put case back back on. Done.
These things aren't antiquities of old, they're just watches, no need to turn a small thing into a big thing.
Plus, in my experience (not with Panerai, granted) the techs that work on your watch are FAR more likely to get fingerprints, dust, hair, fabric particles etc. in the watch than you are. You have a reason to care. To them it's just another watch.
If plexi is wrong, I don't want to be right.