Loot missing from late game Boss Fight

[HeartSail]

Had an issue with the Director Schmector boss fight.
Myself and one other friend were fighting Schmector, we get him down to one hit left.
One of us lands the last hit, and his model disappears.
His ending voice lines play, Wendell comments, we get the achievement for killing him, we get the mutation.
Still no model and nowhere to collect his drops.
Boss fight was completed successfully so there is no way to retry.

If anyone has had and fixed the same or a similar issue please help. I did contact the support team directly but ultimately they don't fix this type of individual player issue.