AI Messed up

[Lord-Of-Shadows]

I am making a map in which i have ships which r really technically flying units because i am making this map for roc. Anyways these ships have the harvest gold/ lumber ability and i made another unit based on a tent which has no pathable building requirements as an oil field and made it a circle of power model and gave it the gold mine ability. The flying ships are supposed to mine those oil fields and return it to oil rigs that they build in the water i used a town hall model for the oil rigs. The oil rigs have the same abilities as a town hall and the ships return to it nicely. Until i build anywhere on the map anohter town hall or another oil rig or resource depository. All of the ships go to the last built one even though there is an oil rig right next to them they will go all the way accross the map to the newest built resource depository. I have tried EVERYTHING to fix this i made the ships from peasant models made the ships fly at first then float once at sea, nothing works. Any ideas or is this a warcraft ai mess up?