Specifically hunting for the Annihilator weapon from Precursor stuff, I've redone the mission about seven times now and haven't seen a single one in the bigger crates, including secret bonus rooms.

I've been doing this for about two hours, just want to get finished with this so I have a more reliable long range weapon since I'm currently using the 'Mercy' weapon and some of the time when firing it there's a chance it just, doesn't shoot the beams.

Thanks.