Postby Arioch » Mon Nov 27, 2017 7:41 am
The AI uses special rules for dealing with metal. Which is to say, if an AI faction finds itself with a metal deficit, it has triggers to take actions to remedy the situation, but it doesn't actually suffer the normal production penalties for being short on metal (it can convert labor to metal at a favorable rate). So I don't think it's a lack of metal that is causing the behavior that you're seeing.
I don't know for sure what the issue is, since this is not really my department, but I would guess that it has more to do with the AI losing large numbers of ships in battles with pirates and other factions, and not having a high enough priority on replacing them.