I know one thread is not enough, there should be a whole forum about bugs and issues with colonies, but this one hit the nerve. Just messed an attack on colony, and had to quit. Sent explorer to find another one. List appeared immediately as usual. But this time it was grayed out and hourglass spinning on it. After about a minute, it disappear. Of course, explorer was on cooldown, and i have no colony to conquer.
Another explorer came home. Tried to send him, but colony search is grayed out.
After refresh, canceled expedition reappeared.