I've noticed on both my dent and Goliath that quite often cap swarms will hit a bot and jostle it but do no damage. It's happened with gemini turrets as well. Both in skirms and just sectors with bots.

From time to time you will find bots that are unkillable - some of it is a lag/comm problem.
In a few cases there health appears to be stuck for some reason.
Until the devs figure it out (and yes its a hard one to find) your best bet is to move on to greener pastures.

I'd say it's over 70% of bots, and only have the issue with missle turrets. I can pop em immediately with cap gauss or undock and kill em with anything I please.

The devs may want to know your complete setup and include a location you know that it happens all the time if possible. Make it as easy as possible for them to recreate the issue,

Easy. Trident or Goliath with Capitol Swarm Turrets. Sit still, get into a turret, and start shooting at the bots attacking the ship. Pick a sector in brac. They all have Arklans which are huge yet do this very frequently.

Oh and bonus info, recently when I Uninstalled and reinstalled VO I tried it with no plug-ins at all. Same results. The only consistent way to make swarms hit is to keep moving at different velocities. I can't just cruise at 15 or 40 or something, it has to be up and down the scale from 0 to 40 and back to 0. Fire a salvo, return to cockpit, accelerate or decelerate a bit, hop in another turret, fire, repeat.

Wow, That is weird. I wonder if the system forgets about you if your not moving....

Bet the devs have some fun figuring it out.

I'm not sure, as to helping the devs figure it out, I'll do anything I can to help. Just don't really know what else to do.

I'll load VO on my tablet and try. See if I get the same results.

Can now confirm the same issue exists on both my Samsung Note 5 and LG G pad 8.0 x.

This issue happens with all NPC's and players alike. This problem has been happening for a while now. Just always forget to mention small bugs.

EDIT: The device you use does not matter either.