In Patton's speech to the Third Army, he refers to an incident in Sicily where 400 men died because a sentry was caught sleeping on the job:
There are four hundred neatly marked graves in Sicily, all because one man went to sleep on the job—but they are German graves, because we caught the bastard asleep before his officer did.
On the scale of the Allied invasion of Sicily, that's fairly substantial -- about 10% of total German deaths -- but none of Wikipedia's articles on the invasion mention it even in passing. Did it happen, and if so, when and where?