I can’t be sure what the problem is.. this comes back to the old tried an true, long testing…
1) deactivate all plugins – if it works then, activate 1 plugin at a time to see the interfering plugin
2) change to WP default them, see if it works
With that said, I have seen that exact same thing, and it’s a known issue (and as far as I know is being looked into)… with the plugin WPGlobus… see here.
Is it random and intermittent in your case?
