[RichD]

This is how an HO track is usually wired.

 

[RichD]

I did not think that the controllers were the issue. If it had been me I would have first disconnected both controllers, then tried them each with both lanes. In my view set type controllers are going to need to be replaced sooner or later if you stick with the hobby. It is OK to change the direction that the cars go around the track by reversing the wires that connect to the power supply as long as you use resistor controllers. As people advance in the hobby they often use electronic controllers, in that case if you switch the wires at the power supply the controller will not work properly and may even be damaged. You would need to switch the wires that connect to each pair of track rails or install a reversing switch for each lane.

 

[RichD]

I don't think that anyone is still making aftermarket controllers with wire wound resistors. All of the ones that I have seen lately use small fixed resistors wired in series. Parma used resistors that have resistance wire wound around a tubular ceramic core, those can take more heat than ordinary fixed resistors. Parma is still in business, but they appear to be selling off what remains of their inventory. A lot of Parma controllers have been sold, they are easy enough to find on ebay.
It is possible to make a variable resistance controller by wiring another resistor in parallel with the main one(es). You should be aware that such a controller will not have a linear response.