The issues you are experiencing with your Pioneer Arms Hellpup are likely due to magazine incompatibility, a known issue with the AK platform in 5.56 NATO caliber, where strict military specifications are absent, and potentially a need for a thorough cleaning and lubrication. ProMags, in particular, are often considered lower quality and known to cause feeding problems.
Potential Fixes and Troubleshooting
Magazine Compatibility is Crucial: The AK platform does not have a universal military standard for magazines, especially in 5.56mm. The original magazine having occasional issues and the ProMags not working at all strongly suggests magazine-related problems.
ProMags: Many users report issues with ProMag products, and they are generally not recommended for reliable function.
Recommended Mags: You may have more success with magazines designed for the FB Radom Beryl or WBP 5.56 AK rifles. Some users in forums have indicated these work, sometimes with minor fitting. Consider checking with a reputable AK parts dealer like Arms of America for compatible WBP or Beryl magazines.

I would def contact: Pioneer Arms @ https://pioneerarmsusa.com/contact

Hi Dan and welcome. I would first contact Pioneer Arms USA for advice/support at: https://pioneerarmsusa.com/contact -- I would also see if any of the suggestions for this model work for you in this series of Hellpup issues/fixes. youtube.com/watch?v=-49p3f5EZWc ----------- Cheers and stay safe!