The mission "A Probe Alone" requires you to bring the ship you find to one of your planets and hanger it to finish. However, the ship cannot be placed into the hanger, so the mission can never be completed.

i had the same problem

In the fleet list, look for the Disband button. Don't use the one that disbands a ship, use the one that disbands a fleet. The ship one's on the far right, the fleet one's in the middle. It's hard to see, I know, a lot of folks are being thrown by this one. :/