I have a Williams Berkshire that I was running on a layout with a CW-80 transformer. Occasionally, the Williams engine ran normally with the CW-80 and other times it would not run at all.
I looked at the track voltage with an oscilloscope and found that the CW-80 would not go to zero volts with the Williams engine with either the transformer handle or the direction button. The engine would cycle into neutral, but would not come out of neutral. The only way I could cycle the engine was to physically remove one of the electrical connections to the track.
The CW-80 open circuit voltage is 55 volts p-p and is a normal sine wave, not chopped. The 'zero' voltage with just the Williams Berkshire on the track is 10 volts p-p and looks like a sine wave with the peaks chopped off. I don't know the technical term for the wave form. It isn't the same as a chopped sine wave.
I then added a lighted caboose to the track which dropped the CW-80 voltage to zero with both the transformer handle and direction button and then I could cycle the Williams engine normally. I recall other posts where users reported similar problems. Adding a small load, such as a lighted car, will correct the problem.
I think the reason that the Williams Berkshire will not cycle whereas my other Williams engine will cycle is because the light on the Williams Berkshire is 'off' when the engine is in neutral. My other Williams engines have the lights illuminated in neutral and probably provide enough load to drop the cycle voltage to zero.