AI bots just camp in fountain in late game Twisted Treeline [Gameplay] [AI]

I've had this 4/4 games. Late game, usually when you start hitting their inhibitor towers, the enemy bots just camp in their fountain instead of fighting.

My repro steps (not sure how broad the bug is, but this is how I have been getting it):

1. Create a custom game on Twisted Treeline.
2. Put two beginner bots on your team and go against three intermediate bots
3. Play as Lux or Veigar (might be any champion, but those are the ones I've been using).
4. Play normally, trying to win.
5. When you hit the inhibitor towers, start paying attention to whether you see the enemy AI players.

Results: You will probably start noticing long absences of enemy champions. Once you're in the base, if you check the fountain, you will see them camping there.