Automotive → 1999 Expedition suddenly won't start

Just bought this vehicle 2 weeks ago. Have no history on it. When test drove/looked at it, none of the issues happened. Drove two different times.
Second time I drove it to work DOOR AJAR light came on, and is staying on, interior lights come on when brakes are applied, rear hatch window will not close (stay latched), and glove box will not stay shut (won't latch).
Had oil changed yesterday and air filter replaced. Stopped at two places on the way back from having it serviced. Started fine.
Today, I sprayed the door locks with WD40 to see if that would cure the DOOR AJAR light issue. I opened and closed the drivers door 4 or 5 times to work in the lube (key was not in the ignition). Got in to start it and see if the code was gone and it will crank and crank but not start.

Battery connections are good, no corrosion, factory key and fob, THEFT light does not stay on in the dash.

I'm fed up already with the rapidly declining health of this vehicle. Please any help will be greatly appreciated.

Have you done anything, like check for spark or fuel?

As for the interior lights/brake light issue, it's more than likely just a bad brake light bulb (filaments shorted together). Start pulling bulbs one by one to see when it stops. If not a bulb, then probably a melted socket.

I have not checked for spark/fuel yet. Got dark before i could work on it.

Thanks for the bulb idea!

Bad ground somewhere, possibly in the tailgate wiring.

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The most likely spot the interior light meets the brake lights is the third brake light. Never made sense that the third brake light comes on with the interior light but it does. It really makes no sense on a expedition but a expedition is just a pickup truck with a built on cap.