launchctl: Path had bad ownership/permissions

I have recently migrated to a new OS X machine, migrating everything from another El Capitan system. My home directory is now on an external drive. Unfortunately, none of my scripts in ~/Library/LaunchAgents is working any more. If I try to load them explicitly, this is what I get:

% launchctl load ~/Library/LaunchAgents/server\ robot.plist

/Volumes/External/Users/peterk/Library/LaunchAgents/server robot.plist: Path had bad ownership/permissions

% ls -l ~/Library/LaunchAgents/server\ robot.plist

-rw-r--r-- 1 peterk staff 642 30 Jul 16:55 /Volumes/External/Users/peterk/Library/LaunchAgents/server robot.plist

The permissions are exactly the same as on the old system, where everything is still working fine.

Could it be to do with the fact that the home directory is on another volume? Or is there something else that could be tried?

Thanks!