I've been having problems with my barley crusher not feeding the grain as well. I think I've found a solution to my problem- I don't know if it is yours as well. I noticed that my non-powered roller was not rolling. When I cleaned the axles of the roller by blowing air around it, it works again for a while.
I think it is a two part problem. First I think malt dust is clogging up the axle by the housing over time, especially when it is humid. Second I noticed that the hopper has a gap on the side where the metal was cut and bent. Sometimes grains will fall through this gap and get between the hopper bottom and the roller. And then sometimes the resistance of having a grain between the hopper and the non-powered roller is enough to stop the roller from moving.
Today I tried my solution. I took out the hopper and placed tape over the gap- on both sides, so there would not be a sticky side open. That way no errant grains would fall the wrong way. I did not have any issues milling today, whereas last time my mill stopped feeding about twenty times. I will have to try it out a few more times to test my hypothesis, but I'm hopeful.