Unless it is something specific to the Extreme, I am running an Apex version and have the RAM clocked at 4000 CL14 using manual timings. If you are using XMP, maybe try using manual mode instead (if you haven't already). Mine will work with XMP, but the system performs better with manual timings and voltage. Using XMP or manual settings, you may need to increase the voltage a little bit. Try 1.360V to 1.400V.
I am not using a bunch of other manual settings for the CPU. The voltage settings for everything except the memory are left on auto.
Wraith // Z790 Apex | 14900KF | 4090 Suprim X+Byksi Block | 48GB DDR5-8600 | Toughpower GF3 1650W | MO-RA3 360 | Hailea HC-500A || O11D XL EVO
Banshee // Z790 Apex Encore | 13900KS | 4090 Gaming OC+Alphacool Block | 48GB DDR5-8600 | RM1200x SHIFT | XT45 1080 Nova || Dark Base Pro 901
Spectre // Z790i Edge | 14900KF | 3090 Ti FTW3 | 48GB DDR5-8200 | RM1000e | EK Nucleus CR360 Direct Die || Prime A21
Methuselah // X79 Rampage IV Gene | Xeon E5 1680V2 | Titan | 32GB DDR3-2400 | GameMax 850W | EK Nucleus CR360 Dark || Prime AP201
Half-Breed // Dell Precision 7720 | BGA CPU Filth+MXM Quadro P5000 | 4K Display | Sub-$500 Grade A Refurb | Nothing to Write Home About