Hello,
As with all things overclocking related XMP is not guaranteed to work plug & play and your mileage may vary depending on the CPU.
Check within the UEFI what VCCSA (System Agent) is being applied by the auto scaling, then increase this value and see if the instability desists.
If the CPU Cores or Cache are overclocked, remove this for the time being also.
Check memory stablity with Karhu Ram Test as this will flag any instability faster than gaming.
https://www.karhusoftware.com/ramtest/
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090