Ok this has been plagued me since GC3 and is a ongoing in GC4.  Basically I'm unable to get free ships from Artifact events or when using stored artifacts from the vault.

I believe this issue is caused by the following:
            If you "Temporarily hide this design" for all core ships within the ship designer screen the game stops spawning the free ships.
This issue could also be affecting Executive orders that spawn ships.

Never an issue in early game where I'm still using core designed ships but as tech improves and I initiate a clean out of designs this issue kicks in.

Can get around this by using filter search and the "Favourite" toggle but every now and then old habits kick in (looking at you 2am late nights)

Cheers Bakka