Distorted hum and sound disappears on Shruthi-1 4PM

I finished my 4PM a couple of weeks ago and it worked perfectly. But when I took it to my friends studio last weekend, suddenly I heard the sound disappear
and finally I heard a very distorted hum. I thought it had to do with the power connector because in some positions of the connector it seems that the hum etc. disappeared. When I switched it off/on, it worked perfectly for a while.
But now, if I switch it on, it works (mostly) perfect, but sometimes when I tweak it, problems come back. Sometimes the sound disappears (or become very soft, including the resonance) but you still hear some triggering of the envelopes.
Does anyone know what this problem could be ?

Thanks !

50/60hz humm from switching/switchmode powersupply perhaps?

Start with the obvious, try another power supply. The centre pin should be nicely snug in the DC jack. You need a DC adaptor made for a 2.1mm pin.

If no good then check soldering on the DC socket.

Ok thanks, I’ll try that !

Things working intermittently might be a sign of weak solder joints.