The reason it is implemented the way it currently is is because without the switching, it would be possible to completely block the border on the other side by simply making a line of creeps stand directly against the border.

You could try using the jump-point algorithm. It wouldn't be very difficult to get it to work with swamps.

You can also access variables defined in your main module.

Sometimes, your memory gets corrupted. It would be useful if you could reset the memory from your profile page. The reset of memory would replace the memory object with:

{
    creeps: {},
    rooms: {},
    spawns:{}
}

http://support.screeps.com/hc/en-us/articles/203013212-Creep#body

This works as expected in simulation mode for me.

I'm having the exact same problem. Logging out and then back in does not help. I even tried restarting my computer. Sometimes, as I'm leaving the survival screen, it'll show a message with my score on it. This only happens with the survival mode ran on the server.

I don't know what your problem is. But maybe TowerStart shouldn't be capitalized at the beginning.