I've changed several older pistols to the soft rubber factory grips. Most of them seem to have an alignment issue on one side or the other.
I don't know if it's the grips or the frame that are different.
I guess the soft rubber grips are easier to install, in spite of the alignment issues, due to being able to push/twist them a little to get a better alignment.
If one side does align well - I install that one last. That leaves me able to get a finger through the frame from the other side to help push/pull/put pressure one the stubborn side.
I also, sometimes, leave the grip "up" off the frame, get the screw started a turn or two (so I know it's straight and threading in without damage to the screw or frame threads) and then start the pushing/twisting action to get the front of the grip down in/on the frame and aligned before using the screw to force the rear of the grip down into place. Again, this might only work with the flexible rubber factory grip panels.
Good luck with it. That can be a frustrating task.