The issue that iIve seen is the application of to much conductive paint to the wheel end of the reisitor... which then through capillary action etc gets under the resistor and shorts the wheelset.
Use CA on the bottom to secure the resistor at a slight angle, this should help prevent that capillary action, and also guve a bit of leeway on the wheel end, then apply a little conductive paint to the tops of the ends of the resistor.