Hello. I also have the problem of black screen for 5 seconds (when fast-forwarding or next chapter) when playing UHD Bluray with menu, both ISO and BDMV. This problem does not occur on 1080p Blurays. I have tested with the Dune-HD connected via AVR Denon x2600h and connected directly to the LG77CX TV. I have the latest firmware installed, in whose changelog it says that this problem had been corrected, but in my case it is not like that (I repeat that only in UHD BD). The truth is that it is quite unpleasant and that problem does not occur when playing the same discs from a Zidoo. I am seriously considering returning the Dune (Pro Vision 4k). Kind regards and sorry for my bad English.