[6AL-4V]

Pictures show APU inlet door open. The APU is typically not started until taxi in.

[jwparkerjr]

I would expect a lot of doors and things to open during the course of that roll out! Good observation though.

[TalonDJ]

Pictures show APU inlet door open. The APU is typically not started until taxi in.

Now that is interesting and indicates engine failure. The systems (or aircraft I am familiar with and very likey this one) will open that door automatically in the case of indications of power failures.