Problem with bolt hold open on 1918 DMW

[Caferacer]

I just picked up a hold open spring from sarco, as it was the last part l needed for my project, and am having the same issue, l wasn't sure if it was the spring or mag causing it, after reading this l think it may be both, l will try doing as you suggested, if a new Mec Gar mag doesn't fix it, thanks