Just flagging what has likely been flagged many times; the Ether Supply public event in the Exodus Black patrol space has been bugged (forever it seems). The Servitor boss will maintain its shield and remain immune despite destroying the first "child" servitor that is connected to it.
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Phoenix AudubonNeed more Salvation's Edge runs! - alt
I've had this happen multiple times to me, as well. It's very inconvenient.