I started receiving Reported benign validator misbehaviour messages and events when I adjusted my genesis chain config.
When I reduced my config to just having whats below things started working, so it was a chain config issue
Process: 30492 ExecStart=/usr/bin/parity --config
/etc/parity/config.toml (code=exited, status=203/EXEC)
I faced a similar issue and had to check parity.service in the git repo. here
The reason was Parity daemon was looking for config.toml file at non-existing path /etc/parity/.
Hope this helps.