SMAX Door Lock Failure

That sounds like a pain. Automatic locks are convenient until they quit. It definitely sounds like an electrical issue, especially if all doors are affected. Have you checked the fuses related to the central locking system? Any chance water got into the door latch area recently?

Fuses are fine. I'm uncertain about water ingress, but I did observe some minor corrosion on what I believe to be the door switch. Could this be a possible indicator?

Corrosion is a big clue! It's likely the cable or plug connection to the switch is defective. Since you're seeing corrosion, the switch itself might be damaged too. While you could try cleaning the contacts, honestly, with electrical stuff, it's usually best to get it checked by someone who knows car electrics. You could make it worse trying to fix it yourself!

I consulted a professional based on the advice and corrosion. The workshop identified a faulty door contact signal stemming from a defective cable connection. The repair cost 95€.