Door lock latch bolt not retracting fully

Most likely failing or not secure on the door. Try tightening screws holding it on, failing that contact manufacturer.

Remove the lock set from the door and take a look what's going on inside. It's really not hard. You undo the screws holding the inside cover plate and handle to the door, and just pull it off. There's a long metal tang that goes through the door from the inner handle to the outer handle, engaging slots in the latch mechanism in the middle. The latch mechanism is a separate piece pushed in from the door edge - you don't need to remove it. Normally when the handle turns, it turns the tang and rotates the latch pull/push mechanism. Turn it with the covering plate off and and you can see what's going on with the latch.

Take it off and see what's wrong.

This was happening to ours last year, and got worse over the course of a month. When I took it off, there was a little tab that had broken/become unwelded. I had to replace the entire unit.

is that a "mortise" lock? you normaly dont see them too much for residential, maybe some older houses though but cool