Annihilus bugged?

CoachLed

Recently I have encountered a few different instances where my Annihilus or an Annihilus that I was fighting was either incinerated or took damage from incinerate (ei fighting Mephisto). Is this a bug or am I missing something? I thought he was supposed to be incinerate immune. Example below:

Patchie93

Pretty sure his cosmic rod needs to be active for the immunity

Karuseus

Yup, he loses those immunities without the rods

CoachLed

Makes sense. Thanks.