I have just had this problem. My in-main-mast-furler from 2010 was blocking (September in Ponta Delagada) due to a broken lip seal. The lip seal did break into pieces, did fall apart and water came in. Because of the lack of a purge (construction fault!) water did stay in the brake in the lower part of the furler cylinder and did corrode the brake up to compolete blocking. I have learned from Amel Yacht Owners Forum that this happens frequently.
I received soon a new furler from Amel (2,5 k€) which has a shaft seal instead of the lip seal and a purge at the bottom. Much better.
Thomas Dargel from Boat&Sail Service in Ponta Delagada did an excellent job in repairing the system for me: He did install 2 shaft seals instead of the lip seal, a purge near the bottom and he did re-activate the corroded brake. It needs a carefull synchronisation with the furler engine . Thomas did also find out the source of the brake and the exact part number. The manufacturer of the furler LEROY SOMER did not sell the brakes separately for selling complete systems. Bad business as usual :-). I did give this information to Maud Tuillaud from SAV AMEL. I give it to everybody who wants to have it.
My decision is for my ship to re-install the old repaired furler - and have the new one as a spare part onboard.
My advice to you is … do the same as Thomas did: Throw away the lip seal and find someone with a lathe to open the top platein a way that you can install 1 or even better 2 shaft seals. Always water runs down the sail exactly on to the middle of the furler engine. The lip sail is not sufficient and a stable solution.
If you require any further details contact me.
SY Oceanica I - Amel54 #156