Uninstall and reinstall memtest - current install may be buggy or corrupted.
Doublecheck motherboard's supported RAM and RAM configurations.
Doublecheck that installed RAM is correct for your motherboard.
Try one module at a time in each available RAM slot.
Narrow down the errors to a particular RAM module or slot.
10,000 errrors:
Buggy/corrupted memtest. One or more faulty RAM slots. One or more faulty RAM modules.
Misconfigured RAM installation.
Ryzen 3900XWhat are the specs for this system?
Memtest86 v8.2 from the memtest websiteWhat "flavor" of memtest did you use? From what site?
Memtest86 v8.2 from the memtest website