Rear passenger turn signal flashing when car is totally off
 

Hi, I got a weird thing: I can not identify what is happening to my 2018 Civic.
The rear passenger turn signal flashes randomly when the car is off and all doors are locked.
I brought my car to the dealer, and they told me that they had checked all lights and connectors and nothing was wrong with them.
They suggest starting with BCM replacement and monitor, which will cost me $650.
I don't understand what is BCM REPLACEMENT and think that even if the BCM was replaced, it would not end the turn signal from flashing. and the future repair job on the same problem would cost me more.

Please advise me if you have any solution. Or should I agree with the dealer service suggestion.

Thank you

There is a MICU in Hondas. It is their brain box for handling body functions like lights and alarms and locks and etc.
It is married into the cabin fuse box.
If the light is blinking with the engine off then it could be the MICU (BCM- body control module)
Or it could be something simple as the column stalk switch is failing
Or it could be a relay stuck (not so sure about this)
Or wiring issue.