Don't know about No. 1 question. Yes on No. 2 question. Don't even try to stick a 20-rd mag in the gun. You might not have enough leverage to yank it back out.
I don't do silencers. And only STANAG mags will fit in that mag well. It doesn't have to be USGI aluminum or steel but it does have to be STANAG. I got a plastic German STANAG mag (Hella) to shoot in my bullpup, but generally I stick with the USGI aluminum mag.Did you fire it without the suppressor on? I'm wondering if the same thing would happen. But yes it is a tight fit on magazines. I only use metal as the manual doesn't recommend plastic magazines. What material mag were you using?
I can't believe they no longer sell these. I'm glad I got mine when I did. I hope you get it worked out.