Ok I've just started adding a simple object pooling system to my game, bullets, enemies and powerups are recycled using a simple arraylist of active objects and a stack of used ones.
And it was looking like I had it working until.. the enemies became unkillable once they were recycled.
The recycling is simply a
go.active = false / ridgidbody.velocity = Vector3.zero
go.active = true
The bullets still work on new enemies and enemies not pooled but it looks like the problem is the enemies, bullets just bounce off them...
It looks like they are not responding to OnCollision events their internal game state looks good health OK update cycle working?