I placed several blueprints before building a logistics network to cover them. The drones in the network will not build any of the entity ghosts from these blueprints. Newly placed ghosts will be built just fine.

I'm not positive if the problem is ghosts older than the drones or ghosts older than the beacons, but it is one of those two.

I'd say it's at least ghosts older than the (in-armour) beacon.

I have the same issue. I placed some Blueprints to layout my Train station and after toggle on the Roboport only some of them were working on building tracks and stuff. And after a longer time only one is working and very slowly.