I found that a button opening a window with section and views navigation will hard lock keyboard navigation by not allowing users to tab, shift-tab, escape, or enter out of the window. If it could be more accessible, this would be a fantastic way to supply step-by-step instructions to an application which is how I first saw it in I believe an ESRI presentation.
In my testing, it is not just the window aspect since I can open a window to immediately focus on the configured close button of the window (Image 1). It also is not section and views navigation widgets broadly since I have used them successfully not in a window. Rearranging the elements in the window does not change the result. Ultimately, pulling all of these widgets and elements together creates something that looks great but seems to hit a brick wall in terms of keyboard navigation (Image 2).
My ESRI ticket confirmed this last week as case #03952209.