Pioneer SX-737 Distortion After 20 mins

I'm looking at this Pioner SX-737 which has distortion on one channel, the distortion starts after 20 minutes of playing.

The only other thing to mention is that this sandcast resistor becomes incredibly hot after only 2 to 3 minutes, so hot that I can't hold my finger on it.

Any ideas guys? Thank you!

And how would a 180k resistor get "incredibly hot"? At even 100V it would be well below 0.1W dissipation.
Interesting, and that's no exaggeration when I say after approximately 2 to 3 minutes from power on, the resistor gradually becomes so hot that I can't hold my finger on it for more than a second or two. You can see burn marks around those traces.

So next is to recap these? Or just the big 1000uf 50v cap? Many thanks to everyone replying and helping me learn!

Awr-057 is a power supply. To understand the function look at the schematic. The 180-ohm 5W resistor is there to reduce the voltage, share the load with the series pass regulating transistor attached to the heatsink.
It’s supposed to get hot, so you are assuming somethings wrong but in fact it’s supposed to be that way and is most likely not the cause of your issue esp if one channel works properly.
On Pioneer big schematics they usually state current drawn from each supply, so you can measure the voltage drop across the 180-ohm to calculate the current drawn.
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