I messaged this as well but then thought it might end up helping someone else if I post it. Feedback is always appreciated if anyone noticed something I wrote that is incorrect or knows something I missed.
There are three points that may leak in your valve assembly.
1. The valve retaining screw oring. This oring goes around the brass piece that screws into the Trracers back bottle valve. Make sure it's slightly oversized and you feed a nice compression when you tighten down your valve retaining screw.
2. The hard plastic cup seal that is on the base of the powertube and the valve retaining screw seals against. If you checked this and the hard plastic seal is smooth then it probably isn't this. This would result in a leak down the barrel. (This is usually the first thing I replace if there is a leak).
3. The small tiny oring that is under the hard plastic seal and wedges between the seal and the brass cup. Might be this oring or it could be the powertube loosening. I would make sure this is tight. It would also result in a leak down the barrel.
And as you mention it could also be the lower pressure in the tank. Try the trracer with a high pressure tank (co2 or hpa) outputting between 650 and 800 psi and see if the leak still exists. Not enough pressure could cause the valve assembly to not seal properly.