I had a few flipped primers when I first started using an rf100, but I kind of learned how to adjust it and it pretty much ran 100% for quite a while. I change between large and small, and the screw that holds the red or blue plastic collar in needs quite a bit of slack, and the clear plastic part needs to be adjusted so anything still upside down has just enough room to drop out.
After a good bit of reliable use, it started to occasionally feed upside down, and it seemed to kind of over excite primers, and jumble them around more than move them through the machine.
The solution was to tighten the big nut on the bottom of the unit like 1/16 a turn. I think the there must be a rubber damper in there that breaks in a little, and it needs to be slightly snug.
That had it back to feeding quickly and never an upside down primer, regardless of where the speed is set (though it runs best slightly above low).