Some time ago we had this ticket resolved: https://ministry.kronosaur.com/record.hexm?id=72188

However only half of the problem was fixed: we now have anti-FF features on point defence devices, but the critical problem that cripples point defence - chasing after dead missiles - still hasn't been addressed. Currently this makes a lot of PD effectively useless, as it will focus on the first incoming projectile long after it's dead...and ignore the next five or so that come in after it. This gets more comical with tracking point defence, where PD projectiles will happily keep tracking a missile that hasn't existed for several ticks.

There's also two longstanding bugs with targetcriteria:

https://ministry.kronosaur.com/record.hexm?id=82410
https://ministry.kronosaur.com/record.hexm?id=6054