Your vm.swappiness=10 is a totally incorrect value for your system.
Set vm.swappiness=60 (based on 8G RAM and 4G SWAP), this way...
sudo -H gedit /etc/sysctl.conf # edit this file
Search for an existing
If found, edit it to say
If not found, add
vm.swappiness=60 at the end of the file
Save your edits and quit gedit
sudo sysctl -p