I had this issue and it was a defective CPU.  I exchanged for another 7700x and everything worked fine (I had two systems so eliminated the ram which was what I thought would be the issue).  If you can't get to 5200 manually, I would suspect the CPU....

Does the system work with stock memory?  Does the system work with CO off?  You need to troubleshoot the setting causing your instability. 

7600 score of 19,9400 is not possible.  And 6.95 is not possible and reporting incorrectly.  For reference 8 core 7700x stock is around 19,500 and with OC memory, CO etc I get 20,600. Sleep kills memory read speeds on wake (drops it to 5200 equivalen...

First, do not use Ryzen Master to OC memory.  Like you, Expo does not work for me but manually setting in BIOS does and has the advantage of allowing better setting for sub-timings than Expo.  For a guide Samsung or Hynix, Buildzoid has some good YT ...

If you reset the bios to default prior to flashing, you would have been at 4800 which is stable for any ram and cpu.