I've seen this twice in my current game (can submit support ticket with save if needed)

   1)  Minor race sends a constructor to a location with both mining resources and a precursor / ascention in range.  Immediately build archeology module.  Never sends second constructor to build mining ring.  Is never able to mine and sell resource.  AI needs to know to send a second constructor to these locations.

   2)  I can not build starbase there because of their starbase.  Sometimes obstructs economic starbase on planet.  They will not sell this starbase too me, despite being deep in my territory.  Suggestion:  make AI more likely to sell immoble assets (starbases, planets) when inside enemy influence.  Now I need to build a fleet to kill the strbases and replace, I would rather buy, esp when deep in my territory.

   3)  Minors go bankrupt, never recover, all production and research stops, including constructors.  Suggestion:  give minors Tourism income at game start (like wealthy perk) so they have a higher initial income.  This may be reason minors never build another constructor.