Channel Manager: Errors when changing channels in edit mode

Errors occur when changing channels, when the channel you are leaving is in edit mode.

Reproducability: 1 out of 10 tries
To reproduce (using Go Green):

• Open a channel in channel manager
• Edit the template
• Click a cross-channel link in the top (language) or change the channel in the channel manager
  Expected: Channel is changed, edit mode is abandoned
  Actual: After a while of waiting, the following error occurs in the UI:
  "The page can not be edited, initialisation of the page context failed."

In Javascript, the following error are observed (copied from Chrome):
The page can not be edited, initialisation of the page context failed. page-editor-all.js:1448
(anonymous function) page-editor-all.js:1448
h.Event.fire ext-all.js:2
h.Observable.fireEvent ext-all.js:2
(anonymous function) page-editor-all.js:791
(anonymous function) ext-base.js:2
Hippo.Future.onFailure future.js:63
(anonymous function) future.js:17
Ext.Ajax.request.failure page-editor-all.js:908
Ext.extend.handleFailure ext-all.js:2
cb.failure ext-wicket-adapter.js:26
handleTransactionResponse ext-base-ajax.js:116
pub.abort ext-base-ajax.js:276
checkTimeout ext-base-ajax.js:147
(anonymous function) ext-base.js:2

Ext.Error
page-editor-all.js:1449
(anonymous function) page-editor-all.js:1449
h.Event.fire ext-all.js:2
h.Observable.fireEvent ext-all.js:2
(anonymous function) page-editor-all.js:791
(anonymous function) ext-base.js:2
Hippo.Future.onFailure future.js:63
(anonymous function) future.js:17
Ext.Ajax.request.failure page-editor-all.js:908
Ext.extend.handleFailure ext-all.js:2
cb.failure ext-wicket-adapter.js:26
handleTransactionResponse ext-base-ajax.js:116
pub.abort ext-base-ajax.js:276
checkTimeout ext-base-ajax.js:147
(anonymous function)