Yes, I've noticed some use cases in hentai where it fails a lot, too. There's suprisingly much upside down scenes or too diagonal body parts in hentai where it stops working, also since hentai has a lot of mosaic censoring it can't really detect those parts. For example, can't make dicks visible (in reverse mode) if they have mosaics on. Black and white hentai manga also doesn't really work very well.