This has happened to me in the past but I neglected to comment on it. At times, I'll send a ship, and it doesn't matter what type but in the below example it's a survey ship, to an area to explore and I'll focus my attention elsewhere and a couple of turns later I'll go to that part of the map to check on the ship and notice that there are gaps in its' path where space has not been exposed despite traveling through it. It's a bit annoying to then have to go back over an area just to expose those areas. In the pic below I had already sent the survey ship back along its' path and it exposed one area already:
