We are using IE but it works on some machine but doesn't work on some machine
If some code works on some browsers but doesn't on other I would strongly recommend checking browser differences first. Perhaps some IE's have compatibility or quirks mode set? Perhaps they have some browser plugins which conflict with CKEditor?
If possible please provide reduced and working sample which we could run and see the problem. Are you able to reproduce this problem without knockout.js to exclude its possible influence on problem?
In page edit mode you create editor instance right after you have started destroying previous one. Could you try doing that after first instance is fully destroyed - http://docs.ckeditor.com/#!/api/CKEDITOR-event-instanceDestroyed and see if it makes any difference? You could also try using this method "on self.closeAndRefresh" - closing the window once editor is destroyed.
