[The other Sean]

Have you checked for leaky rear axle seals? Gear lube on the brake pads or e brake shoes can cause them to get grabby though normally in reverse only.

 

[The other Sean]

As another side note, last spring I was getting a random slip light and locker light flicker (not same issue as you guys are seeing) and my torque pro app was showing no codes at all. When I took it to the dealer, they showed stored codes for the steering angle sensor as well as the rear diff locker sensor, so, it is possible you do have a code, but your scanner is not seeing it.