I have created a custom UI view and when I open it I see in browser console that the application display area grows uncontrollably and
resizeApp function is called in an infinite loop.
aps/PageContainer id in your view clashes with id of some other element in the DOM, most likely a system element
Change the ID of
aps/PageContainer element to a different one, e.g.
<div data-dojo-type="aps/PageContainer" id="pcontainer"> ... </div>
List of DOM element IDs that are used by POA and should not be used in custom UI can be found here.