I had similar issues recently. The dealership wasn't able to find the root of the problem, and there was nothing in stored messages and the scanner didn't show any stored codes.
Finally, I found where the problem grows and fixed the problem.
You need to open the side panel and there you will find 2 modules (green and white boxes) which are the distribution level to all electronic systems connected. So, you need to "shake/move" the wires there, and I bet you will recreate the problem. Ask the dealership to replace these blocks. Also, I have seen a lot of questions here like "service shifter" , sensors messages, brakes messages, etc - in most cases the problems start from these distribution modules.