Small Board

Hi guy my spinning decoy has given up the ghost , used it last week and it was fine , was going out sun put three sets of batteries in and just a hum , opened it up and checked and its not getting the full 6v , I took the diode out to check and seems ok , it has a rotary controller for speed and a switch which runs the motor or motor and led , the motor is fine tested it with 6v and its fine , be great if someone could point me in the right directions as must be something simple , the jack is for remote on via an aux socket on the caller thanks for lookin,PS be gentle I am a novice OAP but trying to learn new tricks lol tks