I have a 2007 7.5m V8 on an X6 mast. the cams, mostly the top one, do not rotate fully around. The rollers seem to be ok and I've tried different cam spacers but the problems persists. 
Any help apprieciated
A bit more downhaul may help.
If you use NP ext and correct mast then at the correct settings you down haul the sail pullies down to near the top of the plastic part of the extension.
If it still doesn't rotate properly after downhauling the guts out of it, you may need to file a bit off the cam spacer on the one that doesn't rotate. This makes the cam not push as hard on the mast so is easier to rotate.
