0.15 is a small amperage. If you are using a clamp meter, it would be tempting to test the accuracy by doubling the loop through the clamp.
If there is a fault to ground, 0.15 amps at 120 volts is about 18 watts. That much heat should be detectable by touch if it all happens at one place. You could try a megger at 250 volts to confirm the problem and pull the lights off the track to eliminate them as a cause.
0.15 amps to ground at 120 volts suggests a ground fault of about 800 ohms, or two faults of about 1600 ohms. It isn't hard to imagine a couple or two with dirt or arcing to be the cause.
I also had problems with track lights that failed at the couplings. It turned out that the ceiling moved when people walked on the second floor.
