I had the same error as you. I also had a rootfs size error where it was dangerously growing towards 100%. I uninstalled the plugin and 300MB out of 16GB were freed. I think the latest version (at least) of the plugin has some issues.
I had the same issue.
Upgrade to 6.9.0 (and 6.9.1 for that matter) and parity was checked at each reboot.
I applied the 100 sec shutdown timeout and it is ok now.