Where does the stderr from launchd go?

Solution 1:

Your second key has a typo in it (has a > before the closing </key>)

                      *
<key>StandardErrorPath></key>
    <string>/Library/Logs/rnamanagedocker_err.log</string>

It should be

<key>StandardErrorPath</key>
    <string>/Library/Logs/rnamanagedocker_err.log</string>

Solution 2:

Try making sure that the system is actually permitted to write to that file. I would suggest simply creating the file in advance (as an empty file). You can do that with the Terminal as follows:

touch /Library/Logs/rnamanagedocker_err.log

Then try first by making the file writable by everyone to see, if that makes it work:

chmod a+w /Library/Logs/rnamanagedocker_err.log

If you want then you can then start limited the permissions on the file to get to the level you require.