Tried out a ferrite on the offending channel and the resulting channel. Did not improve. Swapped the motor caps for wherever else I had on hand. Might be a little better, but it's hard to tell. I do have the motor curve set as a hair trigger which isn't helping. Gonna leave it as is.
Pushed some electronics around under the body. Still a mess. Test fit in the case for an upcoming truck show. Trio of green will be represented, but c308 has to ride on the roof.