I've put in a PR on the screeps engine github repo for this. https://github.com/screeps/engine/pull/5

https://github.com/screeps/engine/commit/a1332ca17ef02ac1f5cef8e22d77d4dea1cfa12c

This will prevent my creeps from withdrawing from my own containers that have no rampart under them if there is a rampart belonging to any other user in the room. 

W3S22

edit: as an added note. I was also seeing this in W1S21. as soon as I deleted the last unowned rampart my creeps could withdraw again. 

That is quite odd then. I remember moving into block E5N55 a few weeks ago. I distinctly remember the 4 corner SK rooms were on the exclusion set. If this is normal though I will go ahead and move on. 

The newly opened map block at W65S65 has a badly configured exclusion area. The 9 center rooms are usually in the initial exclusion. However, it appears that 9 block exclusion was adjusted 2 rooms to the east and 1 room south.