“'Lippage' (the extent to which one tile can be slightly further off the wall/floor than another) is very hard to totally avoid, particularly with certain types of tile. The British Standard BS5385-3 states there is a tolerance of 1mm for joints less than 6mm wide and 2mm for joints of 6mm or more”
I would still be concerned, that had he been more skilled, he would have got it right first time around. He simply might be lacking the skill and experience to get it right, at the second attempt. Hopefully, I am wrong!
No pics yet (floor not set), but the boss was very good about it and agreed it needed redoing. They came off easy enough - maybe not fully set - and by end of day they had redone them. Bit stressful, as they were end of line and in the worst case we'd have had a full-on dispute, not enough spares for a repair, and having to rip it all off. Thankfully it didn't come to that.