Have a MM3 and mill grain for 25 - 30 brews each year. Had this problem a couple of times early on when I started milling for double batches, here is what I have done since without a problem. Start the mill running (I use a variable speed drill with revs set low), then tip a small amount of grain into the hopper to get the rollers going, add a little more and then add the remainder. It seems a lot of grain weight pressing on the rollers may make the it difficult for the idle roller to turn in the bush after sitting for some time. I usually give them a spin prior to milling anyway, but when the hopper is full sometimes if you miss the start and don't get the idlers going, then you have to tip out the hopper and start over. Have tried a few other methods, this works for me, be sure the mill is running then tip in a cupfull or so, slowly add to this to keep the rollers turning then add the remainder.
Rollers/knurling is cleaned periodically, imagine some fine grain dust finds it's way into the bushes so not surprised the mill doesn't run like it did when new. Overall very happy with mine.
Screwy
Rollers/knurling is cleaned periodically, imagine some fine grain dust finds it's way into the bushes so not surprised the mill doesn't run like it did when new. Overall very happy with mine.
Screwy