I had it all apart yesterday and it looks really good inside.  When I tested it again it seemed to have gpm readings jumping around if it was set to like 15 or 20 gpm.  If I set it up to like 40 gpm that it couldn't achieve then it seemed to read more steady.  I  don't think it could be adjusting as fast as it would fluctuate.  I changed settings to slow down those adjustments.