According to https://docs.sencha.com/extjs/6.0/application_architecture
/view_models_data_binding.html
recomendations (Dont create child ViewModels unless they are actually needed) this example should work:

https://fiddle.sencha.com/?fiddle=ucj#fiddle/v7d

Press the 'destroy' button

You see how changing viewModel's property causes an undestroyed binding accessing the destroyed component's setDisabled method which throws an exception.

There is not always so obvious exception as going in this fiddle and most of the time bindings hang in memory causing memory leaks.

ExtJs 6.0.1.250
All browsers