Korg M1 Noisy Output

Hello! I have a Korg M1 that I’m trying to restore. Unfortunately I’m no professional service tech but I love to learn and I’m good with a multimeter and soldering iron. Over the past few months I have gotten everything on my M1 working correctly except the right output and headphone jack. The issue is that my M1’s right line out outputs sound at roughly half the volume of the operational left output jack. Also, the right line out has a very noticeable hum. What’s more is that the M1’s headphone output has the exact same low volume and hum on the right side as well.

I’ve tried reading the service manual to perhaps trace back where an issue might originate from however I’m rather green when it comes to understanding circuit board diagrams. I can trace/follow paths and identify IC’s, resistors, capacitors, etc. with relative ease but I don’t understand much past that.

If anyone can offer some advise on this matter, I would be eternally grateful. Thanks to all who read this and I wish everyone well during this time.

Thank you!