MIWA U9.LA Cylinder does not turn even with key

"I have the key, but I can't open the door because it doesn't stick."

A normal entrance door.I had the key, but the cylinder wouldn't turn.I did the work on the assumption that it was a malfunction such as dirt due to aged deterioration, but it is not improved at all.

I looked into the cylinder with a scope and could not see anything like a foreign object.However, there is a black lump that moves strangely between the tumblers in one place.

The key still sticks, but the cylinder won't turn.After all, I unlocked the door with normal thumbturn unlocking.

After that, when I disassembled it, I found a defect in one of the tumblers.It was because the deformation of the spring caused malfunction.

Since the deformation of the spring could not be improved, it was reassembled using parts from junk items in stock.

Ultimately, the true cause remains unknown.It is a phenomenon that cannot occur without disassembly, so it is probably due to poor work during the reassembly work by another contractor.It is speculated that it has gotten worse over time, but I am not sure.