There is a spring that you pre-tension when you put the gun back together. That should allow you to fix the feeding problem.
The guns are unusual to take apart but a good assembly/disassembly book worked for me.There is also the Video from AGI:
Generally the videos from them are excellent. The usual gunsmith that does them is very organized and explains each and every step. I would think he would cover the tensioning of the internal circular magazine.
Theses are really neat guns and very accurate compared to other lever guns. I really like mine!!