Probably a compatibility issue, I guess.
I think it is either spidertron enchantments or spidertron tiers community, that make spidertron corpse be available to retrieve its content, but this probably cause the giant spider to also be minable.
I would guess it isn't intended for a player to mine a giant spider corpse with op item that doesn't use energy hahahah

I was aware of this issue, but was not sure if or how this can be fixed by only editing my own mod. I implemented a workaround:
If SpidertronEnhancements is enabled:
after spidertron entity dies
find corpses in 100 tiles of killer and remove any that have spider hearts in them

I was thinking we had somthing similar to on_entitty_die, but from this discussion https://forums.factorio.com/viewtopic.php?t=34952, seems like we don't :(

https://github.com/originalfoo/lifecycle-events/blob/master/lifecycle-events.lua#L3

maybe could register to entity destroy and loop over its inventory and delete everything.