Bobby D
You are the first person to mention that as being a possible issue to this ongoing problem. However, the only two engines I have, if I'm right, that have the non-derail mechanism installed are my Railking scale ES44AC designed for sharper curves down to 031 in MTH numbering, and the SD70ACE Veteran Salute engine that comes with a complimenting Caboose accessory. The two ES44AC's that have experienced the problem, at low speed I again want to stress, only have the two pickup wheels at the front and rear. Based on your experience with this type of locomotive, would some rearranging of the rubber wheels help?