e.g. a GA involving a high nose up pitching moment - low engines, max thrust. If the compensating stick forward control continues to be held forward, and still trimming with the expectation that trim will result in zero stick force, then it is conceivable that over correction will continue to lower the nose and the trim positioned nose down, effectively controlling the aircraft. These aircraft require that the stick is moved towards centre to identify in-trim conditions, whereas other trim systems will reduce stick force at the existing control position.
A very strong possibility that this happened in some of them. Coupled with habit of pushing on the stick and trimming only by the tactile feel without reference to ADI it can be a dangerous combination.