I saw this a few times during my playthrough on v0.8.5:







After beating a level (or in this case, after beating the game) the "Your crystal is being attacked" message keeps flashing on the screen.

me too, it seems that it happens if monsters are near the level exit in the crystal phase. The monsters get inside the exit room, and the AI just keeps doing its thing, making combat happen - though it becomes slo-mo before the level closes.

Sometimes the message stays in the 'message buffer' and is displayed at the 'go to next floor' screen.

They've fixed this in 0.8.7