Steps to Reproduce

run the attached example
click the button (observe the logs in the browser console)

Current Result

"onBind" is called 2 times every time the nested added dynamically
"onUnbind" is only called once

Expected Result

"onBind" called only once
(or if technically necessary to call onBind 2x, call onUnbind also 2x)

Unmatched onBind/onUnbind pairs make it difficult to initialize/cleanup client side libraries properly.
The performance overhead of rendering the inner borderlayout 2x should be avoided.

Workaround

Surrounding the inner <borderlayout> with a <div> fixes the problem, and onBind gets only called once as expected