So, we just found an amazing problem on our server regarding running the magento cronjob.
The cron file was run but nothing was scheduled. After much debugging we encountered the following.
For some (magical) reason the cron daemon used the binary in
while the preferred binary should be
so a quick fix was backing up and renaming the binary in
and symlinking the one in local.
This was encountered on a server running DirectAdmin, so if you have a similar problem: check the php version run by your cron daemon!