Error while executing .plist file Path had bad ownership/permissions

Try changing the ownership of the .plist file:

sudo chown root /Library/LaunchDaemons/myfile.plist
sudo chgrp wheel /Library/LaunchDaemons/myfile.plist

or more simply, change the user and group in one command:

sudo chown root:wheel /Library/LaunchDaemons/myfile.plist

It is also worth noting that these root LaunchDaemons can't be world writable, for security reasons:

sudo chmod o-w /Library/LaunchDaemons/*

The plist file must be owned by root and group wheel as rw only for owner. So root:wheel 600

In addition to the above

sudo chmod 600 /directoryToFile/filename.plist

for example:

sudo chmod 600 com.backup.plist

or

sudo chmod 600 /Library/LaunchDaemons/myfile.plist