Marantz Amp. I have a Marantz 6010OSE KI signature amplifier that has a problem. Whenever the

Question

I have a Marantz 6010OSE KI signature amplifier that has a problem. Whenever the amplifier is moved, the left channel stops working, or will only emit very weak sound with no bass. If I tap the side or top of the case eventually it will start working again. Sometimes it will start working again straight away, and at other times it will take quite a few taps before its right. Any ideas?