Assuming that you've already handled this: https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/2/#comment-819173
You definitely want to run a memtest from the Boot Menu (if you're booting via UEFI, you will need to temporarily switch to Legacy mode for Memtest to work or alternatively create a new bootstick via https://www.memtest86.com/
Additionally, if you're going to mix and match memory (which you are), the most stable system is one which
Has all matching sticks
Has matching sticks installed in pairs (this also has a massive performance boost)
If unable to match sticks, then you must ensure the the CL timing is identical between the sticks