This error message/alert appeared immediately after I upgraded to the MCU-2 (bc of eMMC chip failure). No alert prior to chip failure. Alert presented the very first time I put the vehicle into "DRIVE" after the upgrade (was still in the Service Center parking lot).
The alert makes no sense (the vehicle better free roll while driving)...and I thought it would go away with a software update or on its own. I should have taken the vehicle back to the SC to diagnose, but never did. Several months later, message shows up every time it is driven (the messages block other info on the screen).
Although I drove the S for over a month with no displays (before I was able to schedule the MCU install), I don't think I did anything to cause a parking brake related problem.
The new MCU/Service Center visit is probably unrelated to this alert, but the timing makes me suspicious.
I have the very same message on my 2016 Model S. Took it to Service centre and they spent a couple of days trying to diagnose the problem. They charged me over £500 to tell me that they had never come across this error before. They upgraded my MCU1 to an MCU2 (another £1450) only for the problem message to be shown in Orange rather than yellow. No help at all. The only good thing is the car drives perfectly well. I noted I cannot use autopilot or auto park as the message stops these functions. Sometimes it disappears when I park up and then returns as soon as I drive again.