Units getting stuck in tunnels?
January 20, 2009 - 18:34
FinalSun doesn't always save tunnels properly, and as a result, your troops will get stuck in one of the corners. Make sure you test your tunnels extensively and fix all the errors, as it can be frustrating for players if they can't properly use the tunnels.

So after you've made your tunnel, open your map with notepad and go under the "tubes" section. There will be an extra -1 on some of them, where it should have the number before it instead. Change all of the -1's like the pic below: