+1I'm not familiar with the part you added but i'm guessing there is something wrong with that, you installed it wrong or possibly left a part out. Sounds like it's keeping the cartridge interrupter open allowing the spring to just push all the rounds out. The interrupter is the flat part with a slightly curved end on the inside of the receiver that rests up against the shell rim or follower when empty.
Nope, issue is with how it was installed or the part installed is defective.I just bought an OPSol Mini-Clip adapter and some Aguila minishell for my mossberg 500 which I have shot a lot 2 3/4" without any problem. When I pull the forearm to load, ALL the shell in the magazine popped out. Could there be any issue with the mossberg?