Hi Oni
One thing to remember is that for the longest time all the spray cans sold by GW in the US were produced here and were (in some cases) considerably different. The black spray paint fiasco of '06/'07 is a case in point. I was part of the group that tested sample cans from the US manufacturer that were absolutely fine, but I know that the cans that went to market were certainly not the same formulation that we tested earlier.
I've also had a lot of problems with the GWUS Matte Varnish, to the point of not using it for years, but the new Purity Seal is now coming from a central source and is worth a look at. I'd liken it to the old GWUK-supplied Matte Varnish that I used to use back in Australia.
Cheers
Dave