biter spawners are not targetable by turrets when they are spawned from a captive spawner spoiling, and you cant manually shoot it because its remote view

can be solved by breaking the spawner with a landmine, but that also breaks the platform, and you cant repair it if its enclosed

did you try with a rocket turret that have the captive rocket?

yes, could not target it, also to expand on the landmine thing, the hole cant be fixed at all, even when exposed to the outside of the platform

I will investigate. The landmines making holes is sadly/usefully vanilla.
Update: Testing shows they can only be shot with capture rockets.

I'm not sure I want to change it, the nests are a big investment to replace, versus recapturing.

this can be deleted, restarting like 3 times made the game fix itself and now it properly rebuilds the holes when the hole is exposed to outer space
captive spawners spoiling is now just a major inconvenience