Mast head sheaves

I have a F35.
The mainsail is difficult to raise, a friend went up to see it looks like the shaft it revolves on is also turning, looks like it is seized.
I also spoke with a friend of the PO who said both masts have two in mast sheaves and provided a sketch, im trying to send.?
Before I get a rigger can anyone who has experienced similar or who knows what is up there please help.

I recently posted some pictures of my masthead, with an explanation of how the emergency halyard works. See here.

Not sure what sheave they used for the F35, but the masthead on the F36 takes a Harken 500, which is the same as what’s in the mainsheet blocks. However, when I bought my boat I replaced it with a Harken 754 “High-Load Sheave”. It’s stronger, and a bit more sealed, so hopefully it won’t need replacement for quite a while.