It is a very common failure of the 'blue and me' Bluetooth module.
Your options:
1. Do nothing and have the mileage blinking. This could lead to a battery drain eventually.
2. Remove the module and repair it (not difficult but you have to take of a few panels inside the car to get to it then drill out the rivets holding it in place)
3. Disconnect the module and buy a cheapo Amazon Bluetooth receiver as a replacement.
4. Run a proxi alignment using Multi ECUscan to correct the flashing mileage
There are a ton of threads about this exact issue and videos on YouTube of how to access the Blue and Me module.
If you need help, I have done this on my 500 and am happy to answer questions.