It slips randomly. I assume worn or stuck pawls. But it might be a worn sprocket. It's hard to tell, since it is random. I can't trigger the failure to see if one cog slips of it its the whole body. Usually just one power stroke - enough to break stride. And then will behave for a while.

I'll have to try flushing it. I have a sonicator here, so if I can find the removal tool I take it off and flush it out. WD-40 flushing will have to wait until it gets a little warmer (Wind chills are in the range of -5°F!)

If that doesn't work, I'll deal with it later.