Replacing the luggage door lock (cylinder)

[shepd]

Have you tried disassembling it? They corrode internally but 20 minutes with some coarse sandpaper and grease should bring it back to life. The corrosion causes the internal cylinder to get bigger. It then gets "stuck" inside the outer shell and the entire lock seizes (cannot turn it without bending your key, sometimes can't even push the button in at all).

Otherwise, you'll be looking at paying a locksmith to rekey the lock (or having another set of keys just for the hatch).