I have a P4 P+ & usually record in 4K/25. My PC (Win7) handles this okay. However, it won't play 4K/50. It seems to import it okay, but when I try to play it, I just get a black screen. It plays fine on my drone's monitor. I recently increased my RAM from 4 to 8, replaced my power supply with a much larger one, & installed a much more powerful graphics card (it is supposed to process 4K50/60), but this didn't work. Any clues, please?