The present scenario is consistent with malfunctioning hardware.
The recurrent clean install corruption problems are uncommon but are seen with malfunctioning hardware.
Most often it's recurrent unexpected shutdown and restarts or BSOD without operating system corruption.
That's great news that Memtest identified malfunctioning RAM.
There were four RAM modules.
Two were reported old and two reported new.
Which of the modules was malfunctioning?
Check the motherboard for information about using two or three RAM modules and whether there are or are not optimal DIMM then run the computer with either two or three modules and report computer stability / instability.
Decide whether you want to clean install Windows 10 or 11:
Clean Install Windows 10 | Tutorials (tenforums.com)
Download Windows 10 ISO File | Tutorials (tenforums.com)
Download Windows 10 (microsoft.com)
(1) Clean Install Windows 11 Tutorial | Windows 11 Forum (elevenforum.com)
Download Windows 11 (microsoft.com)
Plan:
- Complete Sea Tools drive tests > post images or share links
- Use RAM modules in the optimal DIMMs that have passed Memtest86 testing
- Clean install either Windows 10 or 11 after deleting all partitions and creating an unallocated disk drive
- Install drivers displayed on the Gigabyte and/or component manufacturer websites
- Run Tuneup plus > post a share link into the newest post using one drive, drop box, or google drive
- For any BSOD or unexpected shutdowns and restarts post a new V2 share link into the newest post
- If there are no unexpected shutdowns or restarts and no operating system or component store problems that will complete the troubleshooting
(monitor for 48 hours using Reliability Monitor)
(1) View Reliability History in Windows 11 Tutorial | Windows 11 Forum (elevenforum.com)