I've had no problems with loading 35mm on Paterson reels, but 120 was another story. Much sweating and cursing in the dark! Then I discovered that if I loaded the beginning of the film, the tape which attaches the film to the paper backing seems to stiffen the end just enough to make loading much easier. Gotta be careful, since this means separating the film and the backing paper, with the attendant risk of damage. Of course the reels must be bone dry and clean. I run them through the dishwasher, top rack, every so often.
Stainless steel...another story. Back in the day I loaded Nikkor reels easily and surely, running Ektachrome E2, IRRC, processing five reels at a time of pix shot in London and Paris. Little room for error there! Now, my mojo has deserted me. Same reels, and I struggle, even with the old Honeywell guide thingie. Alas and alack....