It wasn't on my first inmast, but occasionally happened on the 49DS and I've heard of it happening on several other boats. In my case, I re-furled it with less tension on the outhaul and thus it wasn't so compact a roll and filled the space more. The noise when the sail was taken off for the hurricane season was unbearable and I ended up going halfway up the mast, attaching a line to the furling mechanism, and pulling it to the genoa base in order to keep it from banging. Can you tell how much play is in the roller-fuling main? Perhaps you could stuff a towel into the slot and get rid of movement?
it is definitly the furler inside the mast that makes the noise. I must say , in the beginning it didn't make that much of a noise. So I guess it got worse through time. Last winter I took the mainsail off and I had to tie up the alu pipe on which the sail is rolled up because of the racket it made when the mast was slightly moving in the wind.
Infact , is that alu pipe normaly fixed in a certain way on top of the mast ?? I suppose not , the mast wouldn't be able to bent when rigging it up .