Hey mate, i would send it off to Sheriff at LT Paintball. They are the only matrix techs in the country and will take a great deal of care making sure your marker is as good as it can be.
There are a couple of possibilities. If it is leaking out of the back of the bolt then have a look at the number 16 o-rings or the inside of the top hat, in particular the one that seals over the bolt stem.
If it is leaking from the front of the bolt then have a look at the internal orings on the beer can. If it is leaking from inside the front of the bolt then have a look at top hat again.
It may be that your lpr pressure is not quite high enough so tweek it a little. The other possibilty is that you are not using the right lube. Try matrix muck/cinamon butter or white lithium spray from halfords. Too much (within reason) is better than not enough because it will simply shoot through.