I feel like I should apologize, for turning this in to an RC car blog.
I was having some trouble with the Truck cat’s brakes binding on one side. Low speed crawling resulted in the left side track repeatedly locking up. I tracked it down to the brakes, that it uses to steer. My homemade Formica brake shoes had worn more than I thought they had. It’s hard to get a good look at the shoes, when they’re in place, but I noticed a notch worn into one of them. Once I had them out of the truck, I could see the full extent of the damage.