Had the same experiance in mine. Although mine made it all the way to complete shutdown. I'm the autovalve as the Columbus rigs use manual switchover. Flip the gas valve to the other tank, furnace ran like a champ.
I installed the pressure indicator guage gizmos and it helped out somewhat. All they do is tell you your full and than magically, within a very short period of time, your tank is empty. Sooooo look for the beginning of needle movement and that is like a low fuel ligh going off in your car/truck.