I'm only going from watching this YouTube video footage (and the commentary), but it looks like the HE quest blocks got de-spawned while the blocks littered all around them from tech destruction mostly remained in place. (And they were largely dropped before the crate opened.) Crate drop at 17m26s. Return to the same spot at 18:59. I don't know if there's supposed to be an order or precedence, or a default 'first down, first despawned' policy? (Or the reverse?) But either way, I'd think that these quest rewards should have remained, especially given that the blocks around did. Certainly it's worst for them to have vanished than the enemy's parts. Maybe something should be tweaked or refined there. I think it would be sensible to prioritise one's own tech parts too, if that's not already a thing already.