Sorry for the slow reply, been recovering from 2 root canals followed by 2 crowns, I truly appreciate everyone's help.
I will attempt to answer all questions here. I am driving from Michigan to Minnesota with Scouts on Friday on a trip to Boundary Waters. I will be parking my truck for a week and then driving back, hoping to fix my cruise before the trip.
Yes this is one of several ongoing issues. The cruise has been intermittent where it worked but if I turned on defrost, or other functions it shut off, it would act like I stepped on the brake. I've had periods of time where the cruise worked perfectly for weeks. Times it wouldn't work at all, and times it worked and stopped working; very hit or miss.
The rear access pop up glass is now intermittently opening whenever it pleases, even when parked and doors locked.
As a temporary stop gap I pulled the fuse on the rear wiper arm as I learned that also kills the rear access from opening.
I did this because of my upcoming trip, I don't want it opening while I am at Boundary Waters.
The interior is stock, stock radio, etc.
The rear brake lights work
The headlights are "stock" not LED, HELLA H13P50
The rear brake lights are NOT LED.
Both cables that go to the rear lights have been replaced.
The back up lights are LED, I tried switching back to stock bulbs and the cruise still acted up. I thought I had it fixed and posted such and then discovered I wasn't fixed and updated my post.
I have inspected the rear hatch glass and cable numerous times and don't find any issues.
All controls on steering wheel work fine, the cruise on off light goes on and off, just the intermittent cruise control.
I am considering replace the brake light switch (pedal position sensor etc) because my reading leads me to believe this is the most common issue.
My 2014 GMC Yukon XL Denali does not have the brake light switch that attaches with the one bolt on the right of the pedal, here is a pic. Rock Auto and other parts places list the black switch as not compatible with my Yukon, and list brake pedal position sensor #13583374 , I would love to learn I have this wrong.