I think this is a similar bug that has been reported for other units, but I dropped thieves near the guild boat and they stuck there rowing boats.
I can see why, take a look at the wind direction, they have to go in the opposite direction making it very difficult. Rowing a boat is exhausting you know? And they haven't been spending the same amount of time in the gym as the brutes and juggernauts. The bombers use a special bomb to create a huge wave to get them to shore, and I heard the gunners use some dolphins to get to their destination. There are rumors they kidnapped some baby dolphins and blackmail the others to work for them. But the details are all a bit vague..
We're currently investigating this, but we suspect that there may be an issue with the guild ship causing navigation issues for all units, across both platforms. We're looking to fix this asap!
Just had WD get stuck on Guild Ship, waterside just like Bear's post, but on bow of the ship. EDIT: Oops, posted to an Android bug list and this was iPad, but does seem to be all platforms.
yay for Photobucket! finally success. @Lynsey [Midoki] , hope this helps the team fix guild ship sticking.