Is it particular mags that cause a problem ... i.e. P-Mags versus metal ones? The top of p-mag feed areas can be different (more plastic) and stop the mag interfacing properly.
Have you tried firing with pressure applied from different angles? ... so start with pushing up from the bottom of the mag, then tilting backwards and forwards (and even in combination) to see if there's a 'magic position' which allows good feeding.
If you're lucky (it's forwards or backwards) then you'll be able to use something to pack the mag well... I've used Velcro Spots as a good packing thing (to stop stock wobbles etc), but layers of tape could do the same thing. You might lose your tactical reload drop-free-release but that can be a price worth paying.
If it's the mag not sitting up high enough then you're looking at doing something to the mag catch. I've got a problem on my F2000 with (luckily only) one mag - I'm stumped on fixing that though!