If jiggling the batteries make it work temporarily, it's the batteries on their last legs being given a little relief by being disconnected for a short time and recovering fractionally. We used to do that with the transistor radio - turn it off and then on again and it worked briefly, so it couldn't be the batteries right? Change the bloody batteries!
I was called to attend a problem with a TV handset not working. Turned out to be the cheapo corner shop batteries, husband in dog house.