Then we could switch to deutsch...
I have seen this error in some of our customers environments suddenly appear even if really nothing was changed in the template. You can see the exception nearly at the end of the log, I hate this one. I think, your network isn't ready at the moment when the provisioning process tries to download some files from the core. In most cases it helps, when you add a reboot Action with a 100 second timeout as the first action in the system configuration part of the template. Try it and post the results.
Hope it helps.
Schöne Grüße
Christian