recently, I went through The Flush and got the reward chest to appear. as the "animation" played (the chest appearing), the mobs respawned and shredded through my health as soon as I regained control. I think cave mobs' spawning should be paused when the chest is appearing in order to fix this issue
(it was a minor inconvenience because The Flush is near Timasca, and the cave is somewhat short. the same might not be said about other caves)