I had an older house and was installing a new door frame. It seems you could have the frame plumb (hinge side straight up and down) or square (90 degree corners) but not at the same time.
I finally got frustrated and came back with my Porta Power,
a hydraulic jack with extensions and attachments with an
8000 lb capacity, usually used on damaged cars or equipment to bend or force parts back after damage. I was able to convince the wall studs to go back where they belonged to install the door frame correctly.
yep, that’s when you notice how bad it is, when you do a repair or replacement or addition etc.
SMART SOLUTION !!!!!