Can't stabilize DDR5-6000 (ASRock B650M-HDV/M.2)

- Ryzen 5 7600 w/ stock cooler @ PBO 85C
- ASRock B650M-HDV/M.2
- G.SKILL Ripjaws S5 Series 32GB (2 x 16GB) 288-Pin PC RAM DDR5 6000 (PC5 48000) Desktop Memory Model F5-6000J3636F16GX2-RS5K

Basically, while I can POST on the stock JEDEC 4800 MHz, I cannot get consistent POST on anything much higher. When I do clear POST with higher settings, I can run hours of memtest86 always with zero errors. But, eventually on restart, POST will fail the memory training -- 3-beep memory error, and I get reset back to JEDEC 4800. Extremely frustrating.

I did mess up in buying this particular RAM kit, which actually has the Intel XMP Profile rather than AMD EXPO. However, the updated BIOS does provide me with the XMP1 setting, and either way, I'm told ultimately this shouldn't matter - that I should be manually setting timings.

So far I have not had success with most settings. It may have been stable at like, 5200 MHz? But I'm not even certain of that (not enough testing.) But if I can't even get 5400 MHz (90% of my rated spec) it really seems like something is physically wrong? I think I can still RMA my board if I do it somewhat soon.

- Has anyone else here had, or resolved similar issues?
- Can you tell me good timings or things to try (like specific things to set in the BIOS POST memory trainings?)
- Do you think I should RMA my motherboard, RAM, and/or CPU while I still can?

Thanks.