Alright, so this is what i've gathered about the magazine bug.
I was playing with a couple of friends and i was trying out the ArcVR weapons, then i suddenly couldn't draw mags anymore.
I tried fixing it by killing myself and i noticed when you don't move you can still draw mags, but as soon as you move in any direction, you lose the ability to draw mags.
Sometimes i would even lose my arm models for some reason when moving.
My friend (Who was also playing in VR) could still draw mags (He's on a quest, i'm on a vive). Seems like the bug only happens to either the host or vive users, though this is purely speculation.
I tried some other VR weapons that weren't ArcVR and they worked just fine, seems it's only happening to ArcVR weapons.
I tried changing to a custom control scheme, checking if that would fix it but that did nothing.
I also tried different version of ArcVR (OG and Fixed) but the problem still persisted.
Last ditch attempt was changing to a different version of Gmod VR (v20 to v17), didn't work either.
You might be able to keep drawing mags if you use teleport only, but that's obviously boring as hell.
That's all i got.