It's your roller material, and or track/track connection is dirty.
Bettering you connections might help, but in my experience the title of Ole Sparky simply changes hands over time anyhow. The issue usally fades for me over a few weeks/months....and then returns one day, lol.
Pressure per square inch is VERY important for a small electrical connection. The more pressure the easier electrons travel over the connection. Make sure the axle is swedged tight too.
If you just replaced the roller, it my need break in time too. I only oil a new roller if I feel there might be some resistance there. Any major blackness and it gets a flush. Oil is more likely to cause connection weakness. It forms a layer between metals, but usually the lube benefits can easily outweigh the minor connection loss.
