@ADCX Rob, I have never seen or experienced any solenoid based accessory, car, e-unit etc. cause a CW80 foldback unless there were other contributing factors. For curiosity's sake, I did just take three various milk cars and two CW80s I had readily on hand and was unable to cause a foldback condition - it all worked as expected. (However, I can't say I've exhaustively tested every variation of milk car and CW80 that ever existed). Even if the CW80 and its foldback did turn out to be the culprit, that would become a potential suspect following the the troubleshooting questions I offered up earlier:
Does it work on another layout/setup? Does another milk car work on your setup? Does an inspection of the milk car wiring show any concerns and is it correct?
I guess what I am really saying first, is there is not enough information to begin to float a sound theory stating where or what the problem is and that following basic troubleshooting logic will gain meaningful information which can guide a resolution.
Lastly, I'm not saying foldback can't ultimately be the root of the issue, just that I have not seen it to be as prevalent as your posting history indicates it may be.