Hi, here’s Martin again.
It’s the Updates, dude!
Today a fine TS for installing a Windows Server 2012 isn’t running through anymore. After some investigations, it was caused of a Patch/Update, that needs to reboot the System twice. This double reboot can’t be recognized from the SCCM Task Sequence, and after the second boot, the Machine just fails to load the Task Sequence, and will exiting the TS.
Look at this KB Article to solve Problems with those double reboots: