Random [or maybe not] engine coupler opening

I added electro couplers to a loco and had a similar problem. I put .001 uf capacitors on all the switches. ( 2 per switch from the direction terminals to the common. the value is not critical, I used some .003 when I ran out of .001)

I had other locos that never had the problem so it was a surprise when it happened.

   This so far has cured the problem.

  Gunner John recommends putting a capacitor inside the loco. He has had success with that.   Don

A common fix for electrocouplers triggering randomly is to put a 1uf 50V non-polarized capacitor directly across the electrocoupler.  This is only for TMCC, Legacy locomotives already have the protection.

One thing to try before doing any electrical work.  Unplug the electrocoupler from the TMCC electronics and run the consist a few times through the problem areas.  If you still uncouple, you have mechanical coupler problems.  If it doesn't uncouple, I recommend the 1uf cap across the coupler as the first step.