Pilot or trailing truck isolation

[twilight]

Looking for some ideas on isolating the pilot and trailing trucks on my Bowser L-1's. I had test ran them prior to painting and detailing them and I had got them all to run without shorting but now that everything is all back together and looking pretty good the shorting has returned. I am running the locomotives with plastic wheels on the both front and rear trucks. Let me know what some of you guys have come with to solve this problem. Also, I guess I should say that these locomotives are running with NCE decoders in them.


Thanks,

Mark