M38 oil pressure ground?

[TonyMorreale]

1952 M38, 24 volt - Using the jumper test on the oil pressure gauge I determined that I needed a new guage as I couldn't get the gauge to peg. Replaced gauge and had the oil pressure registering at just below 20 at idle, when I gave it gas it would rise to about 60. I let it idle for about 15 minutes and took it around the block to see how it responded only to discovered as I was driving that the gauge doesn't register anymore (past the ignition "on" bump that all the gauges get).

To me this seems like a ground problem... I have sanded the back of the instrument panel to assure good contact and have replaced all four spring clips holding the panel to the dash as well as checking all the connections.

I'm thinking about adding an additional ground line from the oil pressure gauge and was wondering where I should run it from and to. I was going to run it from one of the nuts/posts that hold the gauge in place to somewhere on the firewall behind the panel, but am open to any thoughts from those who might have done this before me.

All other guages and lights work properly - it's just the oil pressure that is acting up.

Suggestions are appreciated. Thanks!