WA Hicap problem
 

I'm having one of the wierdest issues with my WA pistol
I put one mag in, it fires perfectly, and I use a different one I had, and it fires, cycles completely, but when it returns to battery the hammer is decocked, resting on the firing pin again, and I have NO idea how the mag could possibly affect how the sear catches the hammer, and I'm at wits end

any WA aficionados care to throw anything out? also, a while back i saw a site in the US that had droves of info on WA and TM hicaps, but i forget the address, anybody know the site im talking about?