Have two 3 light tracks in Kitchen for past four or so years. High ceilings put in professionally.
Past six months 'one' light on track B was intermittent. Now a second light on track B is also intermittent. Replaced bulbs, did not alter situation. Third light on this track B is working flawlessly. The other three light track on the same electrical line is fine, all lights good.
Have cleaned with 99% rubbing alcohol all the tracks and took a bit of emery for 'one' swipe across contacts, no change.Moving one light module not working to the track with all working does not change, light still won't work in that track.
So is this a transformer 'inside' the light module? I've taken it apart, all wires connected, etc... thanks very much for any help.

Possibly a poor connection where light fixture connects to track. Remove fixture and then reinstall in a slightly different position.

Sometimes the track gets dirty. IN a lot of these units the neutral is connected to the track and that can cause a problem. Call an electrician and have it checked out.

All the tracks have been cleaned. The 'unit' or 'module' doesn't work on another working Track. What "is it" in the module that can go bad individually? I've swapped out the bulbs for new ones, no joy. The lights do come on 'from time to time' and burn normally for a few minutes or longer then dim or go out again. Have moved the module up and down the track... no change in function and, as mentioned, put the suspect modules on another track (which has all three lights functioning perfectly and no joy, bulb remains unlit).

Can I replace just the individual module? Think so and that would appear to be the likely next step?
Thanks again!

It would appear that the light fixture (module) is defective. Probably has a loose connection in it some where. If you can disassemble it you might find the poor connection. Heat probably causes it to make and break. Otherwise your only option is to replace it.