@lionelflyer,
I just finished doing the metal bracket change out on my 2 ZW C units. Both units exhibited severely cracked potentiometer brackets. Lionel is currently showing part # 17 as unavailable and indeed I may have gotten the last pair they had for one of the units just a week or so ago, they had no problem shipping me the parts. But I was short another set.
The good news is that the Trainz store had some. Look for "Lionel metal potentiometer bracket" in their search function. That's where I got the pair for my second unit. Both ZW C's are back in perfect order and I really like them a lot. Hopefully Lionel either is awaiting replenishment on the brackets or they will consider ordering another run to fix this annoying materials defect.
John