Spring stuck in lift arm; Jayco Pop UP

I have a 1996 Jayco Eagle 8 Pop up. The front left (as if being towed) support arm will not extend all the way. I have the camper all the way extended, and it is supported with a 2x4 on the front left end. The problem cable is disconnected.

When I pull the cable to pop up the roof, everything works fine until the larger arm of the lift arm is fully extended, then the cable just completely stops with a hard and distinct thud. I took the spring out, and it looks good to me, but this is the first time I've taken one apart. I don't know how to take off the telescopic lift arm to inspect it. All the pulleys seem to be fine and the cable seems to be routed properly. The spring inside the metal housing seems fine too, I'm pretty sure something is wrong with the lift arm. I looked as best I could down into the lift arm and there is a little metal push ball that looks like something on an adjustable chair leg. I'm not sure if the spring is getting stuck on that, or if that is normal and not part of the problem.

Any suggestions would be great. The short summer season of Alaska is here and I need to get out of the house! Thanks.