When the sail stops coming out, can you see sail cloth stuck in the slot? The first thing I'd try is to lock the outhaul and then use a winch to tighten the furl of the sail around the spindle. I've found this helps when my main jams.
 

When furling, keep tension on the line to ensure the the mainsail is tightly wrapped. Otherwise, it will fill the furling cavity and make for very difficult unfurling. If the sail is jammed in the cavity, grab it by hand to free it.
 
If you have a "solid vang" that is set to angle the boom down, even after creating slack in the topping lift, the sail will be difficult to unfurl. (The topping lift is not needed with a solid boom vang. We use ours to provide additional boom support for the winter cover).  Adjust the vang  by rotating the tube to give the boom a slight upward angle.

Your boat is one hull number from ours and I suspect you have both a topping lift and solid vang, as we do.

Dave-
We have found that the more the boom is raised, the easier it is to unfurl. The trade-off is sail shape.

The rigid vang is constructed like a big turnbuckle: rotate the barrel to adjust the vang length and hence the boom height. I read somewhere in our blog that Catalina used this style boom vang for only a couple of years. I think I also read the boom angle should be about 2-5 degrees.

Also, try adjusting the halyard tension. High tension also impacts the ease of unfurling. 

Dave...

If you replace the bearings in the car, be very careful. I did this and they come with a device to slide the new bearings in. If you simply slide the old car off the boom, you'll have bearings rolling all over the cockpit.
 

I agree with the responses so far. I have always had this problem. If I furl it properly, it does not get stuck in the mast. If it does get bunched up, stuck in the mast, I have to go to the mast and manually pull it out past where it is stuck. If it is furled properly, I usually cannot get the main out simply by pulling out the outhaul through the dodger at the winch, as you would think it should. I found that if I reach up and pull it out from the end of the boom, I can get it started and then there is no problem. I am relatively certain that your block is not the problem. The problem lies elsewhere, I think.

An additional thought.... is your main sail the original? If so it might have stretched and gotten baggy. This can cause the sail to pull unevenly  when unfurling. 

My last, last, thought on this. Had my main get stuck yesterday.

After slightly loosening the tension on the main halyard, it worked fine. I had increased the tension because of wrinkles near the foot of the main but must have over done it. You'd think that having the tension as tight as possible would keep the furler from bending in the mast and allow a straight pull but it doesn't. I knew this from past years but my DRS kicked in and had to relearn the hard way (sore hands from pulling and a lot of foul language).