I restored that game in 2006?12 years ago so there weren’t any Rottendog driver boards at that time but I do see in the picture that it looks like the CPU is not booting.
Try reseating the ribbon cables and other connections between the driver and CPU.
From what I can tell that small ribbon cable might be upside down if the red stripe isn’t on the bottom.

Edited that. Talking about the small ribbon that goes from the driver to the CPU. Also make sure none are a row off.

Yes. Nothing is going to happen until the CPU boots up
The CPU LEDs are all three solid.
When it boots the sequence is different.
One stays on one blinks and the other is off.
Why the CPU isn’t booting at power up can be isolated be as simple as a ribbon cable or other connector being off or more complex if there is a problem with the CPU itself.

How are the batteries? Any green anywhere on them or the chips under?

The ribbon cable is one row off. Look at the picture

Sure is

It is intermittently booting.
When it boots the LED sequence on the CPU is correct and the lights come on then it cuts out.
You may have a low voltage situation or might just need to fish around a bit more with the connectors.
It is probably something simple but I have seen problems like this trace all the way back to to wiring and power service in the home itself.
Might be worth getting the Kahr reset fix since you stated that was a prior issue.

Shouldnt be a prob with rottendog board. But id check the actual voltages at the test points to be sure.

The ground is fine. It looks like it has a newer style plastic speaker panel(WPC-95)so nothing to ground there.
Normally there would be a metal channel which is what the ground braid originally went to.
It's been 12 years but I never like to see anything I worked on in distress if I can help.
Since you are starting to make some progress and mention the sound recheck the ribbon cable that runs from the CPU,to the Fliptronic,sound and dot controller.
That might be suspect as well.
You now know what to look for in terms of proper placement of the ribbon cable and it can be really hard to spot sometimes.

<Sigh> I will never agree with this method of a "fix" You already have a new power board, this leaves only the connector to the power board, the Z connectors, the connector at J210 of the CPU and the J210 header pins 4 and 5 as potential problems.

Reflow J201 pins 4 and 5 and re-punch the CPU power IDC connectors at all 4 points and you will likely be fine.

WARNING: a rant is coming...
FWIW, my STTNG is running on the original 25 year old PDB, with the original capacitors and all original wiring ... including the Z connectors that a lot of folks bypass. The machine was engineered to run this way, and it's not a design flaw as these machines didn't random reboot when they were new, and there is no reason they should require a hack to work now!

This is usually a ribbon cable issue, I would double check ALL of your ribbon cables.

I agree on some level and do not install them on games here but what I have found is that there are power grid problems in some homes that just require it.
I sent a famous actor two games
One was a WPC and the other a WPC-95
both with freshly serviced driver boards and fully tested.
First thing he says is that they look great but both “shut down” when he is playing them.
Long story short he did not have the voltage present at the wall to keep the games from resetting. It was verified by an electrician.
Another time I personally delivered a TAF to a local in the winter same and he was trouble free then once summer came around he started asking about resets.
It was the power draw of his A/C system dipping the voltage. Installed the fix and never heard from him again.
This is what you may not be considering when thinking of the application of the Kahr as a hack. It is something I have experienced several times and all times this was the best and easiest solution if you live in a trouble spot. Some do.

Not really, you have a quick disconnect that's connected to nothing, there should be no quick disconnects on the ground lines and the picture doesnt show where any of the speaker panel ground connections land.

My machine only has a single ground on the speaker panel that goes to the DMD display.

Your game likely has corroded headers/connectors, possibly from exceeding their life expectancy; every time these connectors are taken off and replaced is two mechanical actions against the life expectancy of the part. Both the connectors and header pins were rated to have a life expectancy of 50 cycles...any more than that and the parts plating is expected to be compromised.

The permanent fix is to replace the parts you are reseating.

This is not a fix, but it should get you to the next spaceport.