Possible D.C. To D.C. Converter issue?

So I was selling a GEM and everything worked fine. As soon as the buyer took it home it started developing some strange issues. I don’t have the car In front of me so I’m trying to get some opinions.

Problem #1 the Dash Display turns off when you step on the gas. Like as soon as the current draw go’s up it turns off the display. As soon as you stop the car the display comes back on.

I checked all the connections and all the fuses they were all good.

Today the guy who bought the car texted me to tell me that Now the Headlights and Tail lights are all not working.
This makes me think the D.C. To D.C. Converter has gone bad.

Any thoughts?

Well it turned out to be a Bad D.C converter. It was good that it was a simple swap.