Ghost in the machine?

Is this PW with slide shoe, switches can trigger those.  G

Time to call "The Haunted Collector".  He may not find the cause, but he WILL take that car off your hands! (sadly(?), the show has been cancelled )

Is the car equiped with a thumbtack coupler? Does the thumbtack hang lower than the others in the consist? It could be touching the hot when traversing the switch and triggering the coupler.

Try a piece of tape over the bottom of the thumbtack.

I run several of my old cars this way, and they still work on the uncoupler track.

the coupler does not touch anywhere and the train does not uncouple when I am standing near there..see the video on https://www.youtube.com/watch?v=pOz_-HZdCJA

SPOOKY

irony..the train reports "no Defects"  lol

Here's the fix... Put the car that the knuckle opens  up  next to the caboose or on the RIP track.

There is a severe hump in your track just before the spot where it uncouples.  You can see the cars go up and over this hump in the video.  This will cause the coupler faces to slip against each other vertically and I suspect that this slippage with the drag of the following cars in causing the knuckle to open.  Try some shims to smooth out the grade in that spot.

I just watched your video pop the plastic thumb tack off and bend it up its vibrating down see if that helps.  

Found your problem, you filmed vertically instead of horizontally!

But in all seriousness, I'm going to go with Bob about the up and down of the track giving enough motion to pop the couplers open.  I've seen it on my trains too.

Hmmm same car in nearly same location the second time it uncouples farther past the switch.....a little to "selective randomness" a hump in the track causes the coupler to uncouple?  color me skeptical.....  no other train does it...I am going to turn car around and see if the issue remains....

I just posted another video on Youtube..clearly there is no hump.....https://www.youtube.com/watch?v=ZkGlgT1WVPk&feature=youtu.be

And yes the track configuration has changed but the support has not....and that is what the track is attached to...

"pop the plastic thumb tack off and bend it up..."

I have no idea what that means

I need 8 X 10 color glossies with circles and arrows....

Here is a picture of the coupler plunger take that out and bend it up a bit see if that helps if not your knuckle worn or pin worn but most of the time bending it up works.  

while I have been collecting MTH O since 2002..and these were all bought new, not used..I have recently just started running them...so "wear" is doubtful...I will see if I can see any issue..but the fact still remains when I am near the location, it does not uncouple, but when I am not, it uncouples...seems to me if it was a mechanical defect..it would happen other places on the track.....

Drummer i had brand new cars. I had to do that to some of them bend the plunger up but sometimes it only does it in certain places. I had a new lionel flatcar it would only uncouple in one place but didn't make any sense to me why that only place then i bent the plunger up fixed it and a dealer told me a few years ago to do that if they uncouple. 

Watched the 2nd video-appears that there is a hump. Car in front is higher at hump. Second car at angle and lower. Coupler on rear car slides down slightly. When rear cars levels out, the force of the pull and mis-alignment is enough to separate them.