I think he has a P38?
I don't recall any issues getting mine off, or Dopey's.
I do recall the one on my refurbed transfer box from Ashcrofts kept going until I put the flange in a lathe and polished where the seal goes with some very fine Wet and Dry with a bit of oil. Fine after that but took 2 genuine seals intil I twigged which hurt my wallet.