file down the bb holder (I think that's what it's called) on the top of the mag. It's the thing that holds the bb's in the mag and is on a spring. Shave it down by 0.5mm to 1mm, just take some medium grit sandpaper and file it down no dremel required.
What's happening is your hopup unit isn't pushing far enough down onto the bb holder for it to release the bb's. By shaving it down the hopup doesn't have to go that far in to release.
"Don't you know the first law of physics? Anything fun costs atleast $8"