I have valve covers from a different car that I had powder coated on my car and they are perfect. I don't think the powder coat is your problem. I hope you can get it figured out.
I can't sell my passenger side, I needed to buy yours to take it off. If you find one in a junkyard take the studs off the head as well. I broke one and had to buy an entire head to replace it.
WHTTRSH, I'd be interested in buying the covers you have on your car and I have a stock passenger side cover I could give you if you sell me the covers you have.
My car did the same thing. I pulled the switch out and I squeezed itwhile I turned the lights off , worked fine. I didn't replace it I just tightened a zip tie around it and it works great.