Clutch MC seal gets stuck

[The Veg]

Copper did the trick after annealing them at the MC, but NOT at the SC, which has plenty of flat surface for anything to seal against.

[The Veg]

OK, latest update. I don't think I ever clarified this, but the banjos in question are not on the same hose, not that that detail really matters. The one from the MC to the SC has a banjo up at the MC connection and a 3ANF followed by a 3AN-to-3AN nipple and an aluminium washer at the SC end. This setup was supplied by one of the Usual Suspects (DBE I think) to replace a failed red hose, and the end with all the 3AN stuff has yet to leak. The banjo at the SC is on the hose that goes to the remote-bleed, installed because I don't fancy the idea of having to lift the car and remove the heat shield I made just to bleed the clutch. This is the banjo that has continued to leak no matter what I've tried.

At last count, there were two possibilities: some issue with the banjo or some issue with the SC. Today I tried to figure out which by swapping which connection was in which hole. The result was as clear as daylight: the problem is with the banjo connection. It continued to leak while the 3AN held. One thing I noted was that the 3AN nipple had a MUCH wider surface with which to bear on a washer.