Colony ships sometimes stop at star enroute to designated target.

You may want to check the pathfinding code for colony ships. I have seen a couple of instances now where I have sent one to a tile next to a star I wanted to colonize and it stopped at a star that was directly on the path. This is the kind of problem where I have a hard time trying to figure out just what kind of information might be useful, and it is difficult to figure out a test that will specifically cause the error.

Also, this might have happened to a survey ship, but I am not sure.

Cheers,
Jack