Are you testing the locks from inside? The front doors will open even when locked. The rear doors will open by moving the handle twice. It’s a safety feature.
That’s not the Ford standard interval- that’s whatever your dealer wants to suggest. I’ve seen some still recommending 3K mile changes which is ridiculous.
Ford says IOLM or 10k max for normal service. $5k for severe service. Or something similar. It’s in the OM.
Well you didn’t mention that you replaced the bulbs with LEDs. I bet the bulbs are installed wrong or just don’t work with the edge housing.
Put OEM bulbs in and see if it goes back to normal.
Electronics rarely just stop working after several years unless they are damaged. If they’re defective they fail quickly. 30 yr old vehicles have computers - has parts ever been an issue?
My understanding from Ford engineers is all they can see with a stock tune is how many ignition cycles have occurred. So if you bring it in with 25,000 miles and only 50 key cycles they know it was reflashed. Of course they can see a non stock tune.
FWIW I remember a similar issue on first Gen Fusions that had to do with the engine not stopping in the correct position which caused it to not restart intermittently. I think it was maybe the crankshaft or camshaft position sensor but I really don’t remember.