From Jay: The crash is most likely because parts of the exhibit fences for the Expedition Africa2 and Expedition Africa exhibits are 1 tile away from the map's edge. When they eventually deteriorate, ZT would crash trying to figure out how to get a maintenance worker to fix them. Exhibit fences are not needed against zoo walls, since zoo walls can act like exhibit fences and they do not deteriorate. The following topic at DG has information on this ZT problem:
http://www.ztcdd.org/DG/index.php?topic=5938.0