How are you washing the film after fixing?
Could it be that there is contamination of the developer from chemical carry-over (fixer ?) from the previous developed roll?
I use the JOBO CPP-2 Processor, and the last step is washing (stated as water, 6X at 30 seconds each) which effectively cleans the tank as well as the film.
One thing about "stainless" reels - true, they do not break, but they certainly do bend - and if you have ever tried to straighten and realign one, you know what the definition of frustration is. Plastic *can* break (hasn't happened to me yet) but if it doesn't - it will bounce back - and be "straight".