I tried swapping out R169 with a 4.7Ohm resistor. No change. R50 still had the same current through it. It still has about 320mW of dissipation. I just paralled up two 11ohm 1206 resistors to keep it stable for now. I replaced Q17 and Q18 anyway, and didn't change anything. I checked out everything else around Q17 and Q18 and it looked fine. The only thing I didn't replace is the LM339 comparator (U10), but the pins of the comparator seem to be at the correct voltages.
Update: I ran the board to ~250W out (max of my bench supply and resistors on hand). I ran it for 20 minutes straight with a 50Hz test tone. Everything worked fine with clean output. R50 had a steady power dissipation of ~400mW the entire time. I checked it under the thermal camera, and nothing really got hotter than it did at idle (besides some of the output circuitry as expected). I think I am just going to keep the higher power R50 installed and call it good. I cannot think of any other locations to check besides what has already been checked.
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