1. Exploration: I had @8 ships on "explore universe" and found several unfortunate conditions:

a. many explored sectors showed no in-sector data (no stations) and a few gates found...as if a ship without radar had flown directly from one gate to another...without mapping the all the stations much less the rest of the gates.

b. A command of "explore universe", even with a nearby system only "half explored as explained above", results in the "no more unexplored systems found" and the ship stops executing the command. There are definitely systems left to find/explore. For example: Argon sector Ringo Moon has a north gate leading somewhere but the "explore universe" doesn't seem to have visibility of it.

Workaround: manually fly a ship through that gate.

Edit: most of my explorers were Goner Rangers built from my first Sanctuary.

I ended up switching my explorers to "scan asteroids" which at least gets them into a sector to map it, etc.

I validated that my explorers have duplex scanners but sure there is a possibility that I missed one explorer who flew around without a scanner...but I don't understand how that would affect the rest of the explorers.

(totally off the wall supposition: I aggressively purchased quite a few "sector maps" which gives very basic data similar to what I described in item 1.a above...wondering if a "sector map" somehow sets "mark as explored" for that sector?)