what display are U using? check the cable from switch button to display, some problem exist from broken cable. either cable from switch to display or from motor to display. Also cable for speed sensor.
I'm getting curious with the weakness of this Bafang PCB Board. I got 2 failed already. When I zoomed it there's some moisture on some pins as U can see on my pict. Maybe someone have idea to fix it? or preventing it.