DRBD WFConnection Problem (BOND)

Hello guys,

I had a problem last night. I have DRBD over 2x 10GB crossover links bonded with active-backup.
After I rebooted one host my DRBD had a WFConnection Problem. The Ping is also not working between the DRBD Interfaces.
After doing ifdown and ifup on my DRBD Interfaces the ping works again and after that I started drbd again and it was fine again.

Now my question, why is the bonding active-backup not working like expected after rebooting. That is a real problem and
appeared 2 times in one week (after rebooting)

Please help

Thank you