You want my advice? Try to have the Onkyo repaired. I'm going to do the same with my 2007-era TX-SR605.
I'm in a similar situation, OP, in that I recently bought a Denon X2800 to replace this Onkyo (after it exhibited a steadily-malfunctioning HDMI out, or so I think) and feel like we are not using the capabilities of this seven-channel Atmos AVR. Cost us nearly 1K (via Amazon; no sale prices anywhere else at the time) and I feel like we just don't need its technical prowess, given the fact that we're running a 5.1 system and are totally fine with it.