(from discord chat, I've chopped it down to just give the salient points)

Kinn - Today at 10:19 AM
I've had the "grenades occasionally clip straight through shamblers" bug plenty of times in vanilla quake. I'd totally forgotten it was a thing. Is it still a thing in QS etc?

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c0burn - Today at 8:18 PM
entities are re-used
when an entity is removed, not all fields are cleared
the shambler code sets self.owner = lightningbolt

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[editors note: player then fires a rocket/grenade, spawning a new entity just after the lightning ent has been removed]

c0burn - Today at 8:21 PM
the shamblers .owner field is set to your rocket
so it passes straight through

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c0burn - Today at 8:21 PM
you can just set self.owner = world to fix it
when the bolt is removed
or not set self.owner
really it should be bolt.owner = shambler

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Kinn - Today at 8:27 PM
holky fuck