-[NSAppleScript executeAndReturnError:] gives error with script that works in AppleScript Editor

I'm trying to find out if QuickTime player is paused or playing from Cocoa. I use the following small AppleScript in Script Debugger and AppleScript Editor and it returns true or false as expected:

tell application "QuickTime Player" to tell document 1 to return playing

However, the following code snippet in a Cocoa app isn't working:

NSString *source = @"tell application \"QuickTime Player\" to tell document 1 to return playing";
NSAppleScript *script = [[NSAppleScript alloc] initWithSource:source];
NSDictionary *dict = nil;
NSAppleEventDescriptor *descriptor = [script executeAndReturnError:&dict];

After stepping through the above code my debug console looks like this:

In case it's relevant, it takes about four seconds for the last debugger step, the one assigning a value to descriptor, to execute, which seems very long to me.

I built a simple command line tool app with just the above within the @autorelease block, and it works:

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        NSString *source = @"tell application \"QuickTime Player\" to tell document 1 to get playing";
        NSAppleScript *script = [[NSAppleScript alloc] initWithSource:source];
        NSDictionary *dict = nil;
        NSAppleEventDescriptor *descriptor = [script executeAndReturnError:&dict];

        NSLog(@"%@", descriptor);
        NSLog(@"%@", dict);
    }
    return 0;
}

It's output (when QuickTime Player is running) is:

2014-05-17 11:48:07.255 Sandbox[52872:303] <NSAppleEventDescriptor: 'true'("true")>
2014-05-17 11:48:07.256 Sandbox[52872:303] (null)
Program ended with exit code: 0

Stepping through the sandbox code in the debugger executes that descriptor assignment in less than a second. So what could be different in the app project that is preventing this from working?

It was one of those stupid mistakes that I figured out while my mind worked on it in the background while I worked at other things.

Sandbox. The app is sandboxed and the entitlements give it access to iTunes Apple Events, but I hadn't added QuickTime Player entitlement. The testing app I built wasn't sandboxed, which was why it worked fine.