One of the commercials in the pre-flight block after the safety demo has lots of flashing lights. It is incredibly unpleasant at 6 AM, especially for someone sensitive to this. There is no way to dim or turn off the screen during it unless you did so before it started.

ETA: I am on an A220 and I keep turning off my screen; it has turned itself back on four times so far. I like this AVANT system less and less every time I fly.

-J.