Yes I think that's it. And I thought I had proof that it was the roller but now I'm frustrated. When I took off the front roller which I thought was the culprit the sound didn't go away completely. Then I took off the second front roller and the sound seem to go away but on closer inspection it was still there but seem to be coming from the back truck! I ended up taking off each roller one by one and the sound never completely went away in any case. So either there's a problem with all the rollers or it's not the rollers at all! I am not a very good detective! Here's a close-up video. Can anyone figure it out? By the way the rear unit makes no noise at all when I put it on the track by itself so even though you still hear the sound and the video when the rearunit passes buy real unit passes by it's not coming from that unit.
