Abyss event on map never ends

https://i.imgur.com/XRzWiik.jpeg

I was in Jungle Valley. The event was going ok as usual, but then it never ended. What happened was that 6 mobs would come out at a time, I'd kill them, then 6 more come out. Rinse, repeat. It wasn't a "normal" map - it was a memory. Not sure if that matters.