Crashes in basic property access after iOS 13?

I am getting crashes on very simple object access after upgrading to iOS 13. See examples below. I wonder if there is some change to the language or to default settings in Xcode causing these? Or maybe there is something fundamental that I don't understand about how properties are managed? This code has been reliable for a few iOS versions until now.

EXAMPLE 1: The following snipped crashes when printing _iCloudRoot:

        _iCloudRoot = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];
        if (_iCloudRoot != nil) {
            dispatch_async(dispatch_get_main_queue(), ^{
                NSLog(@"iCloud available at: %@", _iCloudRoot);
                completion(TRUE);
            });
        }

Here is the property declaration:

@property(nonatomic, strong) NSURL * iCloudRoot;

EXAMPLE 2: The following snippet crashes when accessing calling NSURL.path on an object returned through the two member methods

- (NSURL *)localRoot {
    if (_localRoot == nil) {
        NSArray * paths = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
        _localRoot = [paths objectAtIndex:0];
    }
    return _localRoot;
}

- (NSURL *) documentsFolderPath {
    if(_forcedDocRoot) {
        return _forcedDocRoot;
    } else if (self.iCloudAvailable && self.iCloudOn) {
        return [self.iCloudRoot URLByAppendingPathComponent:@"Documents" isDirectory:YES];
    } else {
        return self.localRoot;
    }

}

- (void)loadLocal {
    
    // this crashes on [docRoot path] below...
    NSURL *docRoot = [self documentsFolderPath];
    if(!docRoot) {
        NSLog(@"no doc root!");
        return;
    }

    // this prevents the crash on [docRoot path] below...
    // NSArray * paths = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
    // NSURL *docRoot = [paths objectAtIndex:0];
    
    NSString* filePath = [docRoot path];

Here is the property declaration:

- (NSURL *) documentsFolderPath;
@property(nonatomic, strong) NSURL * localRoot;

Thanks!