I'm seeing this issue too. Specs in profile.
I've just had to replace a 9900k as the first one semi-died and wouldn't boost over 3.6Ghz. BSOD when booting into Windows for anything above 3.6Ghz.
New one just arrived and wouldn't boost when running CPUZ benchmark, single core result was 50% of what it should be.
Closing iCUE and restarting CPUZ sees the single core speed return to expected value.
This is 100% an issue with iCUE.
I'm wondering if this iCUE problem killed my first i9900k..
All BIOS setting stock except XMP is switched on and VCCSA is manually set to 1.20 (Aorus puts it at 1.3v+ which is madness).
This really needs fixing, I used to recommend Corsair products..