JavaScript and dojo: Widget is "caching" previous WIs and failing to render DataGrid

Hello,

We posted a question yesterday and we have made some progress and have narrowed it down a bit - so we are now asking a more precise question.
Our post yesterday - which gives some more background:
https://jazz.net/forum/questions/272454/how-to-use-dojoready-or-dojodomready-with-ewm-custom-presentation

Today, here is where we are:
Using JavaScript and dojo, we've written a non-trivial custom EWM presentation for a customer which extends dijit._Widget and dijit._Templated and uses dojox.grid.DataGrid.

Also, in addition to the DataGrid not rendering we see that this.workingCopy.idLabel equals 3000 for example when we go visit an earlier WI such as 2000.
 
What are we missing? What do we need to do before placeAt()? How do we refresh this.workingCopy to properly reflect the WI we are viewing and to allow the DataGrid to render.

One more observation. As we navigate to different WIs we see that our codes constructor() and postCreate() functions are being called. But if we visit a WI that we have previously visited then the constructor() and postCreate() functions are not being called. The instance is being re-used for the "cached" WI.

Thank you for any and all help or clues.

Regards,
Kevin