1997 Mountaineer Transmission Issue

[shark197MM]

I have a 97 Mercury Mountaineer AWD.
I am trying to solve an intermittent issue with transmission shifting. Maybe someone else who has experienced this too can point me in the right direction.
Out of the blue, my vehicle began staying in 1st gear when I would either first start off, or even during a trip when I would have to stop moving (like at a stop sign).
I took it to a Ford garage and had the transmission screen, fluid, modulator thing replaced....all the usual stuff, with nothing making it better. Ford had a service bulletin about a shifting problem requiring some little "plunger" being replaced, so we did that too. No luck.
I then took it to a private garage, and the fellow took the electronic plugin off the tranny, cleaned it, dried it, and sealed it with some sort of silicon. And the problem went away as mysteriously as it showed up.
About a year went by, and then here it came again, but this time it has not done it except for immediately after starting the engine. Sometimes when it is started, something does not seem to get the signal that the vehicle is moving, and it stays in 1st until I pull over, shut down the engine, and restart. Most of the time 1 restart seems to "reset" the system. I have also "cleared" the issue by removing the + battery lead for about 1/2 hour, which also seems to reset things. However, this is a major pain. The "fix" that "worked" the first go around (cleaning the electrical plugin) has not worked this time around.
Any hints on what might be going on? I imagine that this is not the only 97 Mountaineer in history to have this, and maybe it even happens with Explorers too. I had a 94 Explorer Sport prior to getting the Mountaineer, and never had this though.
This thing is driving me wack because the vehicle runs flawlessly when I do the reset thing (which makes me think nothing mechanical is wrong). I can come home from a trip where I had zero incidents of this, let the vehicle sit in the garage overnight, and in the morning, it may or may not decide it wants to shift without a bout of "resetting" the computer.
Thanks-

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[Billy177]

can you get a picture of the plug that he siliconed up

 

[shark197MM]

I don't have a picture of that plug, but I understand it is the big fat "main one" that is held in place by a bolt.

 

[Billy177]

try unplugging it and spraying it with eletrical contact cleaner

 

[shark197MM]

Thanks, I will try that again. That was the original "fix" that did hold for about a year. I have tried it again recently with no luck this time though. I also took the selector plug for PRNDL apart and cleaned it, and afterwords, the automatic door locks engaged a lot quicker when the vehicle initially moves. The whole thing just hints of "bad connections" in my mind. Like each time I start the vehicle, depending on the quality of all the related electronic interconnections, the computer may or may not get online with all of it's information in place. Any others out there had this mystery?