Why does ADUM6401 power output latch low with power interrupt?

I'm using an ADUM6401CRWZ in conjunction with an ADUM1201WTRZ for isolation to an AD7714YRU A/D circuit.  From a cold start everything comes up no problem but if the main DC power is cycled off/on, 9 times out of 10, the power output of the 6401 will latch low.  Once this happens It takes a longer off cycle to recover.  This is a problem I'm having in the field particularly in startups where power is cycled often.

I'm using an ADUM5401ARWZ on a RS485 without any of these issues.