A:Answer Hi Anthony513, thanks for your question. We're happy to help!
Regarding the UBP-X800M2 and 4K Blu-ray movies, the player outputs video at the refresh rate the disc is mastered in, which for most UHD Blu-rays is 24 frames per second (24Hz).
So, while your television is 120Hz capable, the X800M2 will send a 4K@24Hz signal to your STR-AN1000 receiver. The player doesn't output 4K@120Hz for disc playback. Your TV will then handle the display by matching its refresh rate to the incoming 24Hz signal.
For additional information, please refer to the manual's unit at the following link: https://www.sony.com/electronics/support/res/manuals/4740/043cf5641adf90fb7113c8029fdb0239/47408221M.pdf
Thanks for considering Sony products!
Best regards,
Estefany