[TAPMAN]

I have a 2016 X5 25d F15 model car. At the early of this year, when my wife drove to home it stopped at a traffic lights. it would not re-start again after release the break pedal. Towed to the dealer to check. I have been told the battery supply is not communicated well with the engine. took 5 days in the work shop, then back to work. but the start/stop function was still not working properly as before. most of the time it would not stop now, or 3 days stop and 4 days not stop. whatever in warm or cold of the car. it was the same. no any other appliance used in the same time, such as the heated seat, air conditioning. Battery is fully charged. It's under new the car warranty, but the dealer refused to check it and says it is normal. can any one help?