My entire car was bead blasted down to bare metal and epoxy primed. That's why I don't get it. Hell, there is even rust starting to show on the vibration dampeners which was covered in epoxy black outside of the car before the were installed and spatter painted.
My previous comments withstanding, this doesn't make sense. Unless the blasted parts were allowed to develop some rust before being epoxied, I doubt surface prep is the problem. On the other hand, the rust on the damper looks like it could be the result of insufficient film build of the epoxy or some light rust prior to priming. Paint does not like to cover sharp edges and those same edges are where rust likes to start first.
I would sand it down, epoxy it and spray the whole trunk over with the spatter paint. The spatter paint blends very well so you could tape off all the vertical surfaces to avoid some work. I would not use POR as it is not meant (despite what they claim) for clean metal or for going over existing paint.
