I'm not able to reproduce the errors but I'll try to explain the troubles.
After an upgrade from 8.5.2.201104190003NTF to 8.5.2.201107211551NTF we experience strange errors when partial refreshes are fired. We use a lot of djContentPanes with 'partialRefresh='true' properties. We also try to use them nested, but that does not always work correctly (I wonder why).
We use dijit.Titlepanes to show or hide the djContentpanes, and when the contentpane is shown, the content must be refreshed. But sometimes this generates errors, errors like 'xhr cancelled' in the console. This only happens in the latest version of the Extension Library.
After a while the HTTP taks on the server does not load any Xpage application anymore. When we try to quit the HTTP task, it waits for a lot of requests to be closed. The result is that the HTTP taks does not quit and we have to kill the server before it is useable again.
I'm not sure if you can help us with this issue, but this is preventing us upgrading to the latest Extension Library (8.5.2).