Sony F570ES audio amplifier cracks

Hi ser!

My audio amplifier cracks, recently especially on 's' or 'sh'
sounds, as if the signal was overdriven. Also there are cracks when
the volume knob is adjusted and the left outputs channel mutes
occasionally, and it comes back when I turn the volume higher.

Here are some pics:

http://bksys.at/bernhard/img/x32/-gallery.html

I found 2 overheated resistors (1 watt rating, IMO). When I vacuumed
the dust some of the lacquer broke away, exposing the resistor
material helix, which looks quite ok. The small PCB in picture 4
(dscn7183) fits into the row of holes to the right of the overheated
resistors in picture 1 (dscn7174). It contains the volume adjust
resistor block.

What do you suggest?

Replace the 2 overheated resistors? Should I use 4 instead of each,
two parallel pairs in series, to avoid overheating? Unless I find a
4 W type, if there is such a thing. I don't see any potentiometers
nearby so I guess it wouldn't matter much if the value of the new
resistors differed within the rated tolerance.

Replace the volume resistor block? I'm afraid that might be hard to get.

Or might the fault be somewhere else?

Thank you, Bernhard
.

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