Weird situation with my T480 keyboard-- any troubleshooting ideas?

I have a T480 in overall very good condition. Bought it refurbished a while ago.

I have noticed that for some reason if I press alt + spacebar (the shorcut to change the keyboard backlighting) **sometimes** the keyboard gets blocked.

I have no idea why! This happens only sometimes, so I cannot really pinpoint what triggers it. Everytime I press this shortcut it's a roulette, will it lock the keyboard or not?

The trackpad still works as usual, and the issue dissappears once I reset. I can also use a external keyboard at the time if I want to, but it's obviously not a very nice experience. This happens on both Windows and Linux.

Has something like this happened to someone else? Any tips or suggestions on what to check? I disconnected and recconected the keyboard again, all the connections seemes fine and everything's clean. Do I need a new keyboard?