it seems there is a regularly occuring problems with those upgrades on the md. Sometimes its ok, other times it give the same error as before. Then I will rerun Diskless_CreateTBZ.sh and rebuild the image of the md.
The other thing I noticed today with a kernel upgrade on the core. After the upgrade, I rebooted the server. When it was finished, none of the phones were registered again. So I rebooted the server once more, but still no luck. In the end I had to reinstall Asterisk and now its working again.