Worn rings will absolutely cause fuel dilution of the oil in a diesel engine. Combustion is slightly delayed, some fuel gets by the rings on each power stroke, and oil level rises. Some time later, as oil dilution progresses, and the level is high enough, the engine may not shut off. As sufficient quantities of the fuel/oil dilution is then carried into the combustion chamber past the rings, during fuel rack shutdown. The engine continues to run on. Sometimes at very low idle, sometimes at very high speed depending on the engine and situation. The only way to stop it then is to block the airflow.
From what you've said, I'd guess worn rings as your situation got worse during operation. But just a guess.