I arrived home at 1am on Thursday night after a birthday dinner... and my key card was busted. The unlock flashed green, but then it wouldn't move the bolt in the door. I tried maybe 3 dozen times and then decided to attempt getting help from the limited-english front desk.
This is the picture I took after 20 minutes of watching this dude fiddling with my door doing the exact same thing I had tried for the previous 15 minutes. The master key that fit in the slot below the door snapped while he was trying to turn it.
He soon called a maintenance guy from downstairs (old man, looked like he had been woken up by the call and was not pleased) who just got down to business. He slammed the door with a hammer, waking everyone else on the floor up. Eventually he jimmied the door open!!! I gave him one of my spare boxes of Pepero (빼빼로) for his troubles, and went to bed.