If I read your post you have proper voltage till you turn on the switch?
If that is correct I think you have a short somewhere going out to the light(s). Or one of the lights has really gone bad.
I would bet there is a problem in the wiring between the switch and the lights. Since it is a slide odds are there is a wire that rubbed until it shorted out or just broke off and is shorting to the frame.
Look under the slide, on top and sides while out and partially out to see if you can find the wire that is the problem. If finding none, take off the fixture and look there for a loose wire or broken wire.
A dental type mirror and strong flashlight is really helpful. Good luck!
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