On multi-engine (or even multi-nozzle single-engine) configurations, occasionally RealPlume will spaz out and throw null-refs on every update tick. Only noted in cases where it initially works properly, and then after a few minutes will start to misbehave. Most often this will persist for a few minutes, and then stop; in-game situation changes may have some impact on it, as it is most often noted during ejection and/or insertion burns.
While the NREs are being thrown, particle-effects do not work. The NREs will continue to be thrown even after engines are shutdown and no particles should be being spawned. Once NREs are no longer being thrown, particles resume proper operation if engine is active or activated.