I get all the good stuff so most people think. I had a similar issue on my truck. Let it lose pressure to 0 and then start it and build back up, exact same issue. I swapped out the governor, air drier with new stuff and still had the problem. The issue in my case turned out to be the signal line from the governor to the air drier was plugged at a connecting fitting near the transfer case. It could signal the air drier to dump one way but the pressure was trapped on the other side of the fitting which was clogged with junk. The small line going to the dump valve on the air drier will hold it open for quite a while. I got desperate to move my truck so the grass could be cut underneath it and noticed the signal line still looked very stiff. I put a wrench on it and heard "Phhsh". Ahh, problem solved and the 5 Ton has some newer parts on it.