I'm having similar issues, didn't have many crashes in Windows. I'm getting quite a few errors in memtest. I even disabled my memory overclock. I wonder if Windows was detecting bad sections of memory and not using them, similar to bad hard drives.

EDIT: I found this grub option, gonna try this https://askubuntu.com/a/1227581

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash memtest=4"