I purchased a bnib apex 10 from 3-21. It had the old disc. I was able to get it working fine. If you partially lower the handle while looking at the primer go into the case, you can see exactly what you need to adjust. I also run mine without the plastic cover on my disc. Maybe I'll make a video if I get time.
I did send in for a kit, installed it, need to make different adjustments, but now that's working fine too. Running hand crank slow or fast, haven't had an issue. Autodrive/primer Xpress is next