This are two diagnostics I got before.
matrix-diagnostics-20230718-1035.zip matrix-diagnostics-20230717-2206.zip
Currently I've disabled the ipv6 and everything works fine now. But it is just a temp solution since my bt download require ipv6 access.
Same problem as well. Just want to get clarify: You said restart cannot solve the problem means the webgui and ipv6 are not working once you reboot the unraid or they were not working after sometime you reboot. Mine is the second situation.
BTW, when you are using 11.5, do you have this issue? I'm thinking about roll back to the old stable version...