HDMI-CEC issues with Apple TV

Hello,

I have the problem that my Apple TV can no longer be switched on using the command

"Hey Siri turn on Apple TV in the bedroom".

Strangely enough, switching it off using “Hey Siri turn off Apple TV in the bedroom” works without any problems.

My Apple TV: Apple TV HD (A1625)

My TV: LG 43LH510V-ZE

Switching on had worked in the past. However, with a considerable delay. The TV probably only switched on 10-15 seconds after the command. The TV can be switched on using the Apple TV remote control. It takes a relatively long time for the TV to respond.

However, switching it on, doesn't work via Siri at all. I've already tried everything possible. HDMI cable replaced. TV, Apple TV restarted. Swap the Apple TV in the bedroom with the one in the living room (since it's the latest Apple TV 4K). But that didn't make any difference. I now suspect that it is somehow the TV set as it works perfectly in the living room with my Sony TV. Switching on/off via Siri is very quick here

Maybe someone else has an idea what I could do.