That's a pure Task Scheduler problem, not DSC per se. Something kept the task from running – possibly the server was busy, sleeping, etc. as it notes, you can reconfigure the task to run as soon as the server realizes it missed. I'm not a great Task Scheduler troubleshooter, though.
It's also possible for a large configuration to keep the server busy for longer than 30 minutes. It'd have to be huge, but that could cause a schedule miss if it tried to run and a previous run was still going.
But you'll have to troubleshoot this from a Task perspective.
