timeUnit
Member
Some of the 120 format films I've developed (12) since my October 7 posting demonstrate this issue although others do not. Um.. I've got another film to develop this afternoon, so I'll try timeUnit's agitation suggestion.
It takes a bit of practice to get it totally right. Start with one film in the tank. As you get better, dev. two at a time etc. I seldom need to do more than two.
To get even more random "sloshing", which can be needed when deving two or three rolls at once, try varying the tilting of the tank: right, left, "away" and "towards" yourself. Don't be afraid to make the agitation a bit forceful.