Sortie exterminate melee only weapon does no damage

[thanh20]

Hi. I'm in a sortie mission, exterminate with melee only as a condition. After a while in the mission i found myself in the water using my archwing. Found some enemies in the water, shot them with my archwing primary. After getting out of the water, my weapon dealt no damage to enemies. It was applying status effects but neither they did any damage