Receving 120 and 220 volt readings when testing a home outlet

I recently redid a room in my house (older home built in the 60’s i believe). I decided to replace the outlets as well as they where loose and wouldn’t hold plugs very well. When i pulled a few of the old outlets i found what i looked up to be called “bootleg grounds” on two of the three i replaced. I installed the new plugs without the jumper as they appear to be in conduit boxes and i read the jumper was a really bad idea. I looked up how to test these outlets to be sure the ground is there. (i have a nice fluke multi-meter) When i tested between the two slots i get 120v as expected, now hears where it gets weird and you have to forgive me as im a novice with electricity. when i tested from one slot to the ground hole i also got 120v which i believe is the hot to the ground so that should be expect as well, but when i switch to the other slot to the ground hole i get 220v, which i believe is a big problem, what i want to know is what could be the cause of this so i can try to start hunting this down. Could it be other outlets down the circuit with bootleg grounds causing the voltage to double essentially acting like a 220 circuit? I’m going to start looking for other outlets with the bootleg grounds but i wanted to get more info on this at the same time. Any and all help would be greatly appreciated.

EDIT: I ran around and tested a few more outlets some I’m getting 330 volts at and other 500+ volts..