Ken,(posted 8318 days ago)A few years ago a made a set of rollers and tubes for 8x10 negs from ABS. I had a similar problem, especially when longer development was required. My rollers allowed the tube to travel laterally while it was being rolled. A friend suggested that if the movement was excessive back and forth, the developer would slosh slightly side to side and in the middle their would be an increase in turbulence where the wave fronts met. He was a mechanical engineer, and I don't know if he really knew anything about fluid dynamics, but after I put a couple of stops on each end to hold the tube stationary while rolling the problem was eliminated. If you notice sideways "walking" of the tube this may be your problem.