Not sure, but I believe the bots are acting weird? A second before this, I cleared their entire enemy team, who were all spies. Literally 5 spies, all just jumping up and down in the corner of the glass looking through spawn.
Now, my entire team is spies (except for one engy who hasn't died and respawned as another class yet), and the entire red team is engies, with 6 sentries all built next to each other right outside the lower battlement spawn doors.