Per iX recommendation, please run echo n >/sys/kernel/mm/lru_gen/enabled and see if this helps. You can also add this as a post-init command for it to persist on reboot.
Your graph looks very similar to a known bug that is being fixed with the .1 release coming before the end of this month.
This sounds like a different issue, are you saying this is currently on Cobia and you’re seeing this, or after you upgraded from Cobia?
Since Cobia, system logs are written to the boot-pool. You might see this in some exceptional circumstances if you’re using an exceptionally slow boot drive.