I had issues with my MBUX system as well. First when pairing iPhone to play music using bluetooth, it works at first but eventually completely blocks ability for music pairing to play music. Wouldn't connect over bluetooth. While music didnt' work, voice calls would and it was weird situation until I had to reset to factory from the MBUX menu. When you reset, the zero layer disappears and has the traditional MBUX interface. Then, only after you setup a profile again, MBUX downloads zero layer.
Having all those issues above, jus recently took into the dealer and found out I have a ton of software updates to perform on the car.
With all these software issues, not sure what to conclude about Mercedes over the air updates.