About 20 years ago my trash compactor was squeaking really bad. A friend was over and asked why I didn't lubricate it. I told him I thought it was more than just putting some oil on it. He said "nonsense". He put some oil on it and it stopped squeaking. I listened to that squeak for a couple of years and with just a shot of "3 in one" it was gone.

Never forgot that.

Go up and lubricate it before you think of doing anything further.

On the more involved procedure. From my experience on this boat,, the sheaves at the masthead are probably on the same shaft so if you use one for yourself there's load and you can't pull the shaft unless you do a whole number and use the halyard to raise yourself and then transfer the load to something else releasing the load on all the sheaves.

When you go up to lubricate them you can study how their installed and come up with a plan in case you need to replace them. Take a camera.

As always, I'm right about 25% of the time.

You use a safety line?? From my experience, using a safety line gets so complicated that going up the mast is actually less safe using it.