Immortal Sentinels in Submersible Missions

[Azure.Fang]

After farming Tellurium for the past hour, I've confirmed that there is a rather frequent chance for player Sentinels to be rendered immortal from the start of the mission. Any time a Submersible mission starts with the player underwater in archwing mode, upon leaving the water their Sentinel will be completely invulnerable; UI will show that the Sentinel can take damage (health and shields are colored instead of silver), but they will take no damage from any source. This can be confirmed by swapping to operator mode and going invisible, then observing the Sentinel; enemies will either completely ignore the Sentinel or they will shoot it to absolutely no effect. Dying and reviving at least once resets this condition and renders the Sentinel properly vulnerable.