I agree that a grounding issue seems the most-likely cause for your refurbished 1965 Trailblazer camper's lighting issue.
If the camper was stored for a time after you re-worked the ground wire it is possible that corrosion has developed. We often suggest applying dielectric grease # 11755 at the grounding point both before and after securing the ground wire ring terminal to the trailer frame. The grease blocks moisture and grime that can lead to corrosion. You should not need a second... view full answer...