It is a digital amp, it works at very high frequency, so I don't doubt it leaves high freq artifacts on your power rails.
What overload protection around what relay? I see none of that.The only thing that is tricky is understanding the Overload Protect and circuitry around the relay. I do not see the relay per se - I do see the "open" note next to R29A and C9A. I also see a couple Diodes on the schematic D5A and D6A near the output.