The only thing that comes to mind is the possibility that the reels can move up and down inside the closed developing tank during agitation. In my case I use a single reel tank, and I took a 120 film spool and clipped the rounded ends to make a spacer that prevents my reel from moving up and down. I have never had the problem you describe. If your reels are immobile, then I would try a smaller tank and less vigorous agitation.(posted 8232 days ago)