I had the same or similar problem with my Z950, had the brake switch replaced under warranty,
Now it is running just fine. Chances are your problem is the brake switch.

You need to check out Justin the Creator on Youtube. He has videos showing you how to do many things to the Z950. He will not only show you how to add the signal lights but lists all the parts needed as well and where to get them. I just added signal lights to my Z950, the videos were a great help. It is not difficult at all.