Greetings, I had similar problems.
2016 Acadia Denali. I bought a GM MDI interface and a GDS2 software lease from GM so I could troubleshoot mine. I had many strange electrical problems, culminating with the car not starting. The very first subtle thing I noticed was that the auto up on my driver's window switch stopped working. Then very slow responses to door lock commands and weird things like running lights in one headlight randomly not working. Upon initial diagnosis, I found that almost half of my modules had various communication DTCs set. The other half of the modules simply wouldn't respond when requesting their fault codes. So, after unplugging some modules, rebooting the car by disconnecting the battery, I got all my modules to respond. All of them had communication DTCs set which in themselves do not indicate a problem with that module. One of them had a serious hardware DTC set. It was the first one that misbehaved, the driver door switch module, with an internal checksum error. This code basically means that the module has declared itself insane. So, I experimented by simply unplugging my entire driver's door by pulling the connector at the front door pillar. Wouldn't you know my Acadia sprung back to life, starting and behaving normally with the exception of the drivers door being dead, the radio complaining that its front left speaker was gone and the airbag computer couldn't see the impact sensor in the driver's door. This also confirmed my early suspicion that one insane module was screaming on the bus, annoying all the other modules. Strangely though, after resetting the door switch module several times, and reteaching it where the auto up limit was, my Acadia has been working great for over a week now. I dont trust this module though, so I ordered a new one from Rock Auto for $133. It is supposed to be preprogrammed and it has a 3 year warranty. Made by "Standard" with original Bosch label and part number on it. I will be putting it in tomorrow. I'll update you with my progress ASAP. God bless!