When I experimented with the envoy cruisers as vasari, I queued about 25 envoy cruisers from a desert planet with one frigate factory and rallied them on a neighboring asteroid field.  After about 20 were produced, I looked back at the field and wondered where they all went.  All I saw was one ship.  I thought that was odd, so then I selected the ship and the other 19 vessles instantly popped out of it into the positions where they should have been.  I also noticed this happening with some of the other cruisers like the subverter, however I cannot tell you the exact conditions like the envoy.  I hope this helps.