04 cadillac escalade right side tail light dont work?

why is it that my 04 cadillac escalade rear right tail light dont work......it works when i am on reverse or pushing on the brakes is just that while i am on the road driving at night it stays off while the other one(the right rear tail light) stays on..i've changed all my light buls on that bad tail light but still dont work could you please help me...
04 cadillac escalade right side tail light dont work?
Sounds like the bulb is still bad. They should be 2 filament bulbs and the tail light filament is broken.

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