When I replaced my water pump assembly I noticed similar contact inside the pump cover. I replaced the impeller so I could tell if it was rubbing. Jerry hall recommended shortening the shaft just abit where the impeller bolt tightens on to help secure the impeller better. The one rubber backed washer had worn off letting my impeller move wearing the flat spot allowing play.

I made the mistake of trying to replace certain parts of the water pump, I had to reorder the others wtf was I thinking....Buy all the parts as a whole ...

Good luck ask any questions someone will answer