FreeBSD 11 not booting correctly on PowerPC

I did a source upgrade from 10.3 (installed via CD) to 11p1 (r306420). I followed the steps outlined in "Rebuilding World" and didn't run into any problems or errors. But when I rebooted the system it got stuck in a boot loop. I could get it to boot by entering boot-conf into the loader prompt (for it work I first have to enter show at the prompt).

The boot messages in /var/log/messages don't show anything suspicious.

Any hunches on where to start looking?