I have a Denon AVR-X1200, and recently I have had issues the center channel (dialogue) dropping out. I have only noticed it when I am using D* C61 client which is inputted to Cable/Sat connection using HDMI. It is intermittent in nature. Sometimes I can pause the show/DVR recording and restart, and it will be fine. I have turned everything off, and repowered everything one time also.
Any suggestions to try troubleshooting first. The HDMI cable is new one that is HDCP 2.2/HDMI 2.0a compliant for 4K. This seemed to have started after D* upgraded me for 4K.
Samsung UN65MU8000, C61K
DTV HR 54 with 6 TB External HD, HR 24 in spare rooms
Samsung UBD-K8500 4K UHD Blu-Ray Player, Roku Ultra
Denon AVR X1200W, Klipsch R-28F, R-25C, R-10SW, R-12SW, R-15M, RP-140SA
Samsung UN55HU6950 + SEK-3500U, DTV HR 24, Samsung Soundbar - HW430 - Master Bedroom