It is most likely your original wiring has a weak spot. Sounds like it is probably in the connector, but it could be a broken spot in the wire. Maybe you can try some sort of temporary bypass of the last few inches of the wire and/or the plug. Maybe plug the original light assembly back in an screw it into place and see what happens. It may be your installation finally made a weak spot get worse.
On the other hand, consider the new light. Cheap overseas accessories don't have a warranty for a reason. My LED tail lights already have a few LED's that have gone out and their only a year or so old.
-Jay