Short story is my co worker pulled his tow ball off to steal my 50mm ball . When he removed it , it was loose and hard to remove the nut . Thats because the shank was bent , due to it being a 3/4 shank ball in a 7/8 tounge . He imported the vehicle from Japan and had the towbar installed by toyota

Also we had a major getting the removable tounge out , after said worker said he had it out not so long ago ( transpired to a couple of years ) . It finally came out but is rather rusted and not in good shape .
So keep an eye on your tow balls and make sure they are not loose and if you have a removable tounge either only install it when needed or remove them frequently and rust treat them .
Chris