If 19 came off badly layed, the other will come most likely off too. Take all off and redone. You can start grindering the floor, you risk your floor heating and make all dust for yourself, if you still insist to lay back the 19 pcs, grinder from the back of the tiles which will be pain in the back site but you can gain another 1-2 mm to work with so you need to take less thickness out of the Adhesive on the floor plus you can do the grindering outside. If you laid back the 19 tiles and other 15 comes off 3 months later repeat the procedure. But honestly, better to take all off
