As an electronics tech or engineer it's rare to see the full service manual on the web. Grab this now.
https://docs.sony.com/release/MDSM/989055901_sm.pdf
With that you can scope out the paths and decide what you want to replace. While I am an electronics designer, I don't repair such things when they can be had for 200 bucks. But you seem to be missing this manual so I'll post it here.
I'm about to crack the cover and poke about but have never touched a receiver before. I'm posting to see if there is something I may have missed before doing this and also to be directed for where I should start. I have the service manual.
Here is the issue. The left and right main speakers are both outputting from the right channel and there is no output from the left channel. When running tone test all channels work fine except these two both test to the right channel.
What I have done so far is go through every menu item and set the left channel to the highest offset possible changed all speaker configuration modes from mono to 5/2.1 and then after wasting a few hours testing with individual speakers on all channels to isolate each output I have done a Complete Factory reset and retested to no avail.
I can understand if one channel (op amp circuit) cut out but to have both channels come out of the opposite side is truly baffling me.
Any help would be greatly appreciated.

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