actually my cpu is made in china ( not Malaysia ) i think its better for OC ,,Looks like your X version is from bit better chip bin as should be expected. My needs precisely 1.285 vdd for that fixed 5.5G but its stable there. Even 0.005V more or less is quick bluscreen. Either thats end of the road for my chip or there is one more way.
During ryzen master scanning for suggested undervolt i noticed it tipped different values at different max frequencies. At stock 5150 it suggested -30, at 5350(+200 limit) it was -40.
For my 5.5 fixed OC i used 5350 curve settings as a base with slowly adding clock and voltage step by step. Given ryzen master insight, no wonder this falls apart sharply after certain threshold, especially near edge of chip possibilities.
When I will be in the mood for few tens of reboots i might try again by scraping negative curve, again searching manually if there is anything higher than 5.5 possible and only then search again for new negative curve.
Either way I won't complain. I was lucky with memory kit too. Cheap kingston sticks only rated for cl40 tightened up at cl28 with tight other timings, certainly not expected that when buying it. It is tearing through my use cases, not planning any upgrade until last supported am5 line along with whole different ddr5 kits available by then.
Userbenchmark is funny too, it gives funny description of your system. Mine is "UFO" and " operated by technical master " comparing performance to typical for given parts.
also I never use ryzen master ... BIOS setting all the time
btw what is your ram type ? die ? you may need further tuning