Your leak could be a sticking solenoid.
Remove the air source and dry fire it 5-6 times, and listen for the solenoid to click. That should reset it.
If that does not work, I would try taking the solenoid apart and cleaning it. Reassemble it dry and see if that helps.
My TM7 had the same problem, and that is how I fixed it. It happens once in a while especially if it has been sitting.
This is on the upgraded version that is not supposed to do this as well.