BuildPlayer for iOS - progress bar never closes

Every time I build and run on the iPhone I have to force quit Unity when I return to it. The progress bar (see image) never closes and no other windows are active, including the “quit” option under File. Is there something that needs to happen in Xcode to inform Unity it’s job is done? This happens in multiple projects.
(OSX 10.11.6, Xcode 8.0, Unity 5.4, iOS 9 and iOS10)

I can see and scroll the error console window.
0 Errors
18 Warnings in build “unknown file ext: [jar, meta, xml] Unity Editor.HostView:onGUI()”

A second project has no errors or warnings but still hangs after a successful build.