Bbshd controller showing 11v less then the actual voltage from battery

[Gytis2k11]

Hi all recently i got a barely used bbshd controller that had all wires snapped off. Apparently it went in to front sprocket, thats the story from the owner. He said the controller was working fine. So I soldered all the connections as it should be and plugged in a 57.8v battery (52v) once display was powered on i was seeing 46.4v on the display. I changed the voltage on the display, flashed the firmware with few different versions, tried 3 displays and 3 batteries and still same issue. Dissasembled the controller to look for any damaged components but couldn't find nothing. Did anyone had a similar issue and could tell me some clues on where to find the components responsible for this