BMW 320d f31
Hi I have a 2013 bmw 320d f31. I was driving in traffic and my car was working fine until I came to a stop and the engine cut out due to it having stop start fitted. When I tried to set off the engine would not start. I tried several times to start the engine with no success and then to make it worse I started getting a electrical burning smell in the car. So I phoned the r.a.c who came out and said it was the alternator that was the cause. So I had this replaced wich wasn't cheap if just been out in the car and the exact same thing happened again. I also forgot to mention the car keeps displaying a message saying it has an ignition fault. Does anybody know what might be causing this or experienced this before?