How to locate thread 1 exc bad exception error - finding light switch in a dark room
<p>OK, in a general sense, this suggests a UI (main thread) usage of a junk variable either by miscount retainCount or uninitialized, but how to find where?</p>

<p>In my case I have an app window with several tabs, each of which nib loads a view. Recently when one of these selected, and the view/nib is loaded I get this:
<a href="https://i.stack.imgur.com/0WaJT.png" rel="nofollow"><img src="https://i.stack.imgur.com/0WaJT.png" alt="Stack view"></a></p>

<p>this model had been working for years.  What's new? Xcode 8, a weather module used by items in the view where the failure occurs.  I've littered breaks everywhere but I'm trying to see a stack which apparently this isn't detailed enough. Does the stack show a "description" was sent to a bogus object?
<a href="https://i.stack.imgur.com/1shzn.png" rel="nofollow"><img src="https://i.stack.imgur.com/1shzn.png" alt="NSApplication stack"></a></p>