TTThumbsviewcontroller stops loading thumbnails

I have the problem that my TTThumbsViewController stops loading new thumbnails after a certain amount of thumbnails. This number changes but is always above 50 thumbs.

There is no more button displayed or something like that - it just isn't loading the thumbs, but displaying the gray border and also the size of the table would be OK.

Is there a download size limitation in Three20 or a limitat开发者_StackOverflow中文版ion how many thumbnails can be loaded at a time or any other reaons why it's possible that not all thumbnails are loaded?

Thanks for you help!

- (void)load:(TTURLRequestCachePolicy)cachePolicy more:(BOOL)more
 {
    if (!self.isLoading && TTIsStringWithAnyText(_url))
   {

   }

 }

(NSInteger)maxPhotoIndex {
    return _photos.count-1;
}