All the responses you received so far are very good especially with regards to making sure the Paterson reels are very clean and dry and the problems related to using a changing bag.

If you are having trouble getting the film started on the reel and it takes too long this will add to your frustration and the humidity build up.

Here is a simple trick to get the film started on the reel.
It gives the stiffness and guide to get the roll started in to the flanges...

Cut a piece of the film box to be the same width as 120 film and about 2 or 3 inches long.

Before you go in the darkroom, or changing bag, slide this piece of card along the reel tracks into the beginning of the reel but not past the little ball bearings. Now when in the darkroom take your film and slide it along the card until it is past the ball bearings and pull in a bit more then remove the card and load in the normal way. You see the card acts like a guide and makes those springy films easier to get started.

I most often reverse curl the first 1/2 inch or so of my film before loading to help with the springiness.
I still have the same bit of card I cut out of a Fuji box a couple of years ago, I only replace it if it gets lost or too banged up.



Don't give up on Paterson reels, I have used them for 40 years or more and never had problems with 120 film I have plenty of reels so I always have dry ones and after each development job I give the flanges a scrub with hot water and an old toothbrush. I have stainless reels too and I can load them without too much trouble but I learnt on Paterson reels so stuck with them.