Kevin most likely scenerio that happened was binding in pivot and not letting the inching rod release and gave the operator the sense that the transmission had internal problem. I usually find this to happen in severe duty trucks where the trans overheat light comes on due to truck being used as a forkdozer or operater that likes to ride the inching pedal. Trying to get unit to move they probably started actuating the directional lever slowly (THE) or hard shifted and produced the code. As units transmission warms up the binding increases. I have found that reassembly after clean out using food grade grease ( the thick tan kind ) on shaft eliminates black gum build up. Be sure to install new o-rings on shaft during reassembly. Some models were equipped with grease zerts on pivot shaft.