You can turn on, or off, the sound with the tiny lever that sits on top of the round battery check light. This lever is hardly visible and some never knew it exists. It could be that this lever is causing your problem and perhaps, by moving it from left to right a couple of times, you solve your problem. Just in case you don't know: when face the front of the camera, the light sits under the OM-4 letters left of the lens
If that's not the cause, I would take it to a good photoshop before finding a repairer. Perhaps the batteries are the problem
Does your camera shoot and transport normally at the mechanical 60? I have had several problems with two OM4Ti bodies, which I believe to be caused by severe humidity.