I am using Jobo Expert Drum for 4x5 processing. Often I have the problem with uneven processing. There are areas on the bottom part of the negative, usually right next to the edge, which seems to receieve no chemistry. Strikingly, sometimes they clearly received developer but did not get the fixer. I always load the film dry, then prewet for two minutes and proceed to processing. I use the drum on unicolor roller. I will appreciate any advice to solve this pretty frustrating issue.