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.