MIWA WEST916.LA, the indoor key sometimes does not turn.

"Sometimes the thumbturn doesn't turn."

This content is not enough information. When we arrived at the site, we found that it was a fairly old property. The cylinder set seems to be the "MIWA LAMA" type.

I checked the operation of the thumbturn with the front door open, and it was working normally. If so, is this the strike position? It seems like it's subtly interfering with the deadbolt. There doesn't seem to be much adjustment range, but I moved the strike as much as possible and completed the adjustment. It would have been nice to have a little more leeway in machining dimensions during construction, but it looks like the strike was installed at the last-minute machining position.