Sometimes there is no answer to explain why something does or does not work. Back when I was working we made some parts that were pretty hard as in hardness of the metal, not complicated hard. When we tapped the holes they all were too small and the inspection gage would not screw into them. These were 1-1/4" diameter threads. An old guy like me, I was young and stupid but I knew it all, told me to put a shop red rag over the hole and then screw the tap back into the hole and take the rag with it. All holes fit the gage after doing this. I do not have a clue as to why that worked. Glad it is staying where you want it now.