Swap not being used
Increasing swappiness fixed it. The swap was enabled, but for some reason only used when the memory was completely full, and no sooner.
Don't think so.
First check cat /etc/fstab for your swap partition, then try formatting the swap file system with
sudo swapoff -asudo /sbin/mkswap /dev/sd##sudo swapon -a
In my case I installed another Ubuntu test instance and formatted the swap for it, so the UUID of the swap device was old in fstab, I just changed it to current and it works.