Do you have an old raspberry pi or laptop? Netbootxyz will run on a potato with ethernet.

I have NetBoot.xyz on my network for ipxe booting. They have memtest as a boot image, ran that for a few days. I don’t remember if it found the stick that was bad or if I just started pulling and booting and process of elimination.

Have you made sure your ram modules are all good? Was getting funky behavior with truenas in a proxmox vm, come to find out one of my 32gb sticks was bad. Removed the stick, no funky behavior. Replaced with a different stick, been solid since, maybe a year and a half on now.