I had this issue as well multiple times after towing through the mountains. Last time it happened it didn't fix itself like previous occurrences. I have upgraded to 5.13 gears after the first incident and just decided to go with the ZAutomotive Z Locker OEM which fixed the issue and it hasn't...
Same thing happened to me today while towing trailer downhill at about 60-65mph.
Rear locker showed as engaged and automatically disengaged itself a few minutes later.
I've had nothing but good experiences with Quadratec. I've found their estimated ship dates to be pretty accurate.
I've also had good experiences getting in touch with them via online chat through their website when I had questions.