The tenders are both Lionel 6466WX so they both have two rollers, one on each truck. They are essentially identical.
Rob, I added electrical tape. I should have stated, when I had this tender on the track by itself, there is a hum coming from it. I added the tape but it did not change anything. The second tender did not hum at all when it was on the track. It seems to run fine.
I'll start working on rewiring the malfunctioning tender later this week. She may become, what maintenance in the Air Force calls a cann bird. Meaning cannibalization. I might just use her for parts.