I have the same problem off and on with my reel. When it was new, the dealer adjusted a screw on the guide rollers/pulleys that feed into the drum, and the screw tightened those rollers up so they made a tighter connection. That helped a little, but never totally solved the problem. I talked to the owner of Glendinning at Quartzite a few years ago, and he said I needed to take those rollers/pulleys off and clean/re-tighten them. I haven't looked at the reel recently but I seem to remember those rollers/pulleys.
I find that when it doesn't want to feed, if I extend the cord a foot or two and restart it for puling in, that usually helps. Sometimes I have to do it forward/back a couple times to get it going.
Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra