For anyone else having this problem in the future (Fix at the bottom, description in the middle):
Symptoms: Everything works fine after a reboot but after "extended" uptime (1-2 days) the error would occur and unraid would show 100% memory usage in the "Log" section.
Problem: After some days of testing I believe that the issue may be that unraid is unable to handle stale websocket connections. Like when you're putting your computer to sleep the connection doesn't get terminated by your browser since it doesn't actually quit, it just gets frozen.
Solution: What fixed it for me was to always log out of unraid, therefore properly closing the websockets, before putting my PC/Laptop to sleep/hibernate.