Dan's advice is all sound. However, I'd submit that we don't have enough information to give any sound suggestions. All we know is a mk2 VQ trigger has been installed in something. Is the something a mk1/mk2/mk3 or a mk4? What other mods has this pistol had done? The devil is in the details.
From posts #1 and #7, I'd tend to think the pistol is a mk4. If so, the problem is the frame is tapered in front of the trigger. The newer VQ mk4 trigger is also tapered to work properly in that frame. A mk2 trigger would need to be modified to work right.
If the pistol is a mk2, I'd be checking the trigger bar (disconnector) for straightness. And the trigger bar may need some small mods, depending on what other changes have been made to this pistol.
Please provide us with more information so we can give you better advice.