Workers fail with kernel panic

Every attempt to build my branched packages fails with a kernel panic:

    7s] booting kvm...
    7s] linux64 /usr/bin/qemu-kvm -nodefaults -no-reboot -nographic -vga none -object rng-random,filename=/dev/random,id=rng0 -device virtio-rng-pci,rng=rng0 -runas qemu -cpu host -net none -kernel /var/cache/obs/worker/root_5/.mount/boot/kernel -initrd /var/cache/obs/worker/root_5/.mount/boot/initrd -append root=/dev/disk/by-id/virtio-0 rootfstype=ext3 rootflags=data=writeback,nobarrier,commit=150,noatime panic=1 quiet no-kvmclock nmi_watchdog=0 rw rd.driver.pre=binfmt_misc elevator=noop console=ttyS0 init=/.build/build -m 8192 -drive file=/var/cache/obs/worker/root_5/root,format=raw,if=none,id=disk,serial=0,cache=unsafe -device virtio-blk-pci,drive=disk -drive file=/var/cache/obs/worker/root_5/swap,format=raw,if=none,id=swap,serial=1,cache=unsafe -device virtio-blk-pci,drive=swap -serial stdio -smp 8
   12s]     2.700679] Failed to find cpu0 device node
   14s] /bin/bash: error while lo    4.957923] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
   14s]     4.957923] 
   14s]     4.959928] CPU: 7 PID: 1 Comm: build Not tainted 4.7.3-1-default #1
   14s]     4.960714] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20160215_214832-lamb16 04/01/2014
   14s]     4.960714]  00000000 f50e7f14 c053fa8c f50e4040 f50e7f20 c035dfc7 f50e7f20 f50e4040
   14s]     4.960714]  f50e7f20 f50e4040 f50e7f64 c025da3a c09f1f60 00007f00 bf856fc4 f36d32a0
   14s]     4.960714]  00000000 f50e4544 f50a8c00 f50e4040 00000001 f50e4540 c0c834c0 c03cc4ad
   14s]     4.960714] Call Trace:
   14s]     4.960714]  <c021baa2>] try_stack_unwind+0x142/0x150
   14s]     4.960714]  <c021ace9>] dump_trace+0x49/0x1b0
   14s]     4.960714]  <c021baf6>] show_trace_log_lvl+0x46/0x50
   14s]     4.960714]  <c021af1b>] show_stack_log_lvl+0xcb/0x110
   14s]     4.960714]  <c021bb87>] show_stack+0x27/0x50
   14s]     4.960714]  <c053fa8c>] dump_stack+0x55/0x79
   14s]     4.960714]  <c035dfc7>] panic+0x8e/0x1c6
   14s]     4.960714]  <c025da3a>] do_exit+0xa4a/0xa50
   14s]     4.960714]  <c025dab7>] do_group_exit+0x37/0x90
   14s]     4.960714]  <c025db26>] SyS_exit_group+0x16/0x20
   14s]     4.960714]  <c020198e>] do_int80_syscall_32+0x5e/0xc0
   14s]     4.960714]  <c082a7a1>] entry_INT80_32+0x31/0x31
   14s]     4.960714] DWARF2 unwinder stuck at restore_all+0x0/0x1a
   14s]     4.960714] 
   14s]     4.960714] Leftover inexact backtrace:
   14s]     4.960714] 
   14s]     4.960714] Kernel Offset: disabled
   15s]     4.960714] Rebooting in 1 seconds..### WATCHDOG MARKER END ###
   15s] No buildstatus set, either the base system is broken (kernel/initrd/udev/glibc/bash/perl)
   15s] or the build host has a kernel or hardware problem...

gave up after 9 failed build attempts...

Did I do something wrong or is there a problem with the OS the qemu machines are using?

Something was repaired and now everything succeeded.