I really can't find an example of a RDC being used successfully and reliably as an impromptu locomotive. Again, I think the problem is the use of hydraulic drive that is similar in concept to an automotive torque converter. They'll pull themselves, but even the RDC-9 trailers were half powered.
Ironically, the earlier gas-electric cars, or "doodlebugs," were often used to pull unpowered trailer coaches, and once passenger service had ended, some were even used as switchers. However, it's worth noting that some of those cars were very similar in concept to early diesel electric locomotives. Electromotive build gas-electric cars before GM bought the company and went into the locomotive business.
Budd cars are different beasts and won't stand that sort of abuse. The Quebec North Shore & Labrador tried to pull a dome coach between a couple of RDCs, but it's worth noting that was just about the time they ceased RDC operations. So, did they have problems? All I can say for sure is that today they run a conventional locomotive hauled mixed train. No more RDCs.