I'll try running loco's and flexing the controller lead to see if that reproduces the fault.
Would an increased load on the system reproduce this kind of fault. I'm thinking, I have an incline on the layout about 3 deg, the class 37 is slowing down towards the top of the incline, the class 37 has internal lighting as well. Is there any way of checking the current being drawn. Just realized that the fault occurred when the class 37 was stationary.