Kuva thrall fell through floor and was stuck in "awaiting mercy" state under stairs

[oohshiny]

On Helene, Saturn during a Kuva Lich defense mission, a thrall fell through the floor / under the stairs during the last wave and was stuck in the "awaiting mercy" state. There was no way to progress the mission to completion apart from the host quitting (forcing a host migration) which reset the squad to the start of the last wave again.