Exactly same issue here.
S/PDIF works while rebooting and stops when reboot is finished and KPA is on.
Ditto - Exactly the same here.
Works fine while booting then stops when KPA is booted up. 
Exactly same issue here.
S/PDIF works while rebooting and stops when reboot is finished and KPA is on.
Ditto - Exactly the same here.
Works fine while booting then stops when KPA is booted up.