To be serious for a minute (and I hate being serious), the amendment would be a key thing if I was in your slippers.  If they let me amend the 2021 return, that's a sign that they just didn't know what they were doing and are willing to do the right thing ------ they would be a keeper.  If they don't want to amend, time to throw them back in the lake for some other tax preparer to reel in.