Left channel sound low and hissing

The left channel is not changing volume and is stuck at being very low, it is also quite fuzzy. I can only hear any sound from the keys on that channel if I turn the volume all the way down as this stops any sound coming from the right channel.

This applies to the inbuilt speakers and the headphone port.

I’ve replaced all the capacitors and even the amp but it hasn’t fixed the issue. I think there might be a short somewhere on the board before the output is split but I can’t see anything.