The mount can't be adjusted. This is a lens issue.
First thing I would do is examine the lens closely, looking (listening) for eg loose elements, and signs that the lens has been tampered with like slight scratching of screws, the lens spanner slots on the nameplate.
I don't have this particular lens. I posted in the
adaptall club thread about adjusting infinity focus on the 28A. In fact I later noticed that the problem was a loose front element. in any case pulling off the rubber and seeing if there is an easy adjustment is a first recourse. Have a look and post a pic or two and we can try to advise...