Trailer brake intermittent
This may sound crazy, but if it didn't happen to me just yesterday I wouldn't believe it.
Getting same readings as you on my 2015 Chev 2500 with HD Tow and factory integrated BC.. Just yesterday.
After checking everything 2x. I pulled out truck owner manual (always a last resort)
It said to un plug TT from receptacle, turn off TV wait five min start over and I be damned it reset and all was good.
Not saying this is your problem, but worked for me, and I'm still amazed at the internal workings of these complex systems....they simply talk to one another.
Try it......nothing to lose. Or consult your TV manual if you have integrated system. If not may be a moot point. Good luck..