Batch render "Time Limit" fails horribly

Hey guys,
After a long time I did a batch render in 3.6 with Progressive on and time limit set to 180 minutes. I left it overnight to have renders prepared for a meeting in the morning.

Well… Apparently it was a bad idea because this combination has failed me again. After 11 hours, when I got to my computer, it flashed, and started rendering the second image. This was not the first time and I still can’t find the cause of this problem. Not using Progressive seems more reliable minus control over time spent.

Any ideas?

Yes, the sleep mode is disabled.