I have the same unit & have had issues like yours asa well. It turned out that there is HDMI Video control settings. If you go Settings>HDMI>HDMI Video Format>HDMI Video Format again., you can & should set to "Mode 2" Remember at this point you can change the Video format for each input as Target source is the choice before HDMI Video Format. I didn't know this was changeable to each source & sent a perfectly good unit out for repair because of operator error. You want to make sure that the input that is giving you issues is set to "Mode 2". Now that being said HDMI is very finicky & I have had to occasionally reset the receiver with initialization function. Settings>Function>Initialization. Probably gets hosed after a firmware update. Sometimes I go to turn on this input (Set-top box) & I get no sound so I do an initialization reset. If it still is hosed turn everything off (set-top box, receiver) & back on again. So my settings are: make sure you have HDMI Control "On" - ARC "On". I have Standby Sync to Auto, 4K Upscaling to "On" & Standby Through to "On". Also in Sound> DTS Mode, make sure to have Mode 2 set. Hope this helps. I posted my issue on this forum but have not posted my resolution yet.