The set is not faulty.
The assembly/alignment is most likely causing a common conductivity problem, which still happens here occasionally.
Get out a ruler and measure if track is properly alligned along edges and distance apart.
Here place a small dab of vasoline on each rail connector when assembling , while others favor jumper wires.
Also personally use a flat track only, no over and unders.
Clean the rails occasionally.
Track is never placed on carpet and not walked over or bent.
Even a track set on a table, with the excitement of racing, can become out of alignment.