Thanks David. I'm in Morocco so it's always sunny! Further checks reveal all holders working perfectly. Images attained with Fomapan and T-Max and 180mm lens all good. I've covered the top of the camera with the dark cloth for exposures made in bright sun. The only two possible areas for the problem source are: I have switched to using a different box of T-max 100 and I have not used the 300mm Nikkor. These are the only two possibles. In terms of tank issues and fix. The conclusion I've reached is that Fomapan suffers from no issues of the film backing not clearing on back to back loaded images whilst the T-max often does. As per your suggestion I'm opening on clearing and adjusting the films slightly to free them up and fixing for a further 3 mins. I am also washing as per Ilford's recommended low water usage of 10, 20 and 30 inversions as I do not have a clear running water supply. Attached: Fomapan 200, rated at 100, f5.6, 1/15. 10 mins, 20 degrees. Pyrocat. T-max 100, rated at 64. f11, 1/30.