BUG: Can't complete quest that requires defeating O.R.C guards at Milk Molar Stash

[goobstomper]

I got to the part of the signals and stashes mission to defeat the orc guards at a milk molar stash. I got to the milk molar stash and killed the Orb Weaver Jr.'s Then the regular Orb Weaver got distracted by my ant and disappeared. Ever since the that Orb Weaver disappeared, I haven't been able to complete the quest. The marker still shows up there, but nothing spawns, and the quest shows as incomplete. I've tried loading up back-up saves but that hasn't worked.  

[Marisa Silvia]

This same thing happened me as well

[Isaac Rasmussen]

Same sort of thing but at the blueberry patch, a bee glitched under the ground and de spawned because I couldn’t kill it.