First thing, I think that without the resources and tips listed here I would have gone insane because none of the youtube videos are very good and it definitely took quite a bit of tinkering. Very easy to get it to only flip a few every 100, harder to get it almost perfect.
After playing with the primer drop insert, the clear cover at the top of the ramp, the rheostat, and putting the RF-100 on a gun mat as opposed to directly on a wood bench, I have it working reliably. I ran a couple thousand primers through (well 100 primers a lot of times) after finding a reliable setting and only had 1 primer flip. Definitely good enough for me not to have to watch it run.
I've seen a lot of people getting frustrated with the RF-100's and I can tell you that 30 minutes to an hour of your time is well worth never having to manually fill primers or deal with a flip tray and a vibraprime ever again.
It is stated in other older threads but...
1. Make sure the insert is loose - for me the screw almost touches the top edge of the primer tube when it is inserted
2. Adjust the clear cover (over the last portion of the primer ramp) toward the outside of the primer ramp until primers won't enter, then very slowly adjust inward until they will just start going through and tighten down snug.
3. Rheostat - for me using the lowest setting was the best, if I turn it up much it starts to flip primers. Most people use between lowest and slightly above the lowest setting
4. May depend on your primers, but for me having it on a gun mat (or a small mouse pad) helped smooth things out
5. the loud vibrating that comes and goes at times is the spring in the insert on the base (what you set the primer tube on) vibrating against its housing and is NOT the screw touching the top of the primer tube i.e. nothing you need to "fix".