Some days later, the tedium of cutting down a massive project is finally rewarded. The code was using a method of opening a document that perhaps is no longer supported? // problem somehow associated with this line of code // maybe the GPU is not cleaned out properly??? [self openNewDocumentIfNeeded]; Once that line was commented out, the problem went away. In case one might spend more time wondering why .... ? ... then here is the offending code segment // this code segment is from https://stackoverflow.com/questions/7564290/why-isnt-applicationshouldopenuntitledfile-being-called (void) openNewDocumentIfNeeded { // Get the recent documents NSDocumentController * controller = [NSDocumentController sharedDocumentController]; NSArray * documents = [controller recentDocumentURLs]; // how many documents are in the recent list // .. the most recent document added is at the bottom of the list // ... but somehow I've noticed that the order of documents in the list can change int nRecents = (int)[documents count]; // If there is a recent document, try to open it. if ( nRecents > 0 ) { NSError * error = nil; NSURL * url = [documents objectAtIndex:(nRecents-1)]; [[NSDocumentController sharedDocumentController] openDocumentWithContentsOfURL:url display:YES completionHandler:(void (^)(NSDocument * document, BOOL documentWasAlreadyOpen, NSError * error ) ) ^{ ; }]; // If there was no error, then prevent untitled from appearing. if ( error == nil ) { if ( nRecents > 0 ) { return; } } } // Open an untitled document what if there is no document. (restored, opened). if ( nRecents == 0 ){ [[NSDocumentController sharedDocumentController] openUntitledDocumentAndDisplay:YES error: nil]; } }