Briefly my set-up is a Panasonic Viera TV (HDMI2/ARC) linked to a Yamaha AMP on the output with the 5000T connected to the Yamaha on HDMI2. Other connections are an Xbox on HDMI1 and a Freesat 1000S on HDMI3.
When the 5000T (with CEC enabled) is switched on it powers on the TV via CEC and then the TV powers on the AMP using ARC. This works fine during the day but every morning the TV fails to switch-on via CEC so it has to be done manually from the TV control, after that if you standby the TV the AMP and 5000T switch off and powering on the 5000T switches on the TV and AMP.
I have made various changes to the AMP/TV set-up to try and fix this overnight problem but no success.
The only thing I can think of is if the overnight housekeeping on the 5000T is doing somthing to stop CEC working.
The Freesat 1000S box always worked without any issues so I'm fairly convinced the issue is with the 5000T.
I know CEC and ARC can be a bit flakey but any suggestions appreciated.