I agree with the criticism about the huge time gap. That plot hole immediately jumped up at me at first.
During the later parts of the trial, they heavily imply Eva needed to know the EXACT second Diana walked into the room so she can trigger the trap right after. It kind of makes me think whether there was some miscommunication among the writers surrounding the evidence.
It would make much more sense if the note Diana received told her to go there in the middle of the tournament. Or if the trap was triggered around 9:10-ish at the latest.