Soundbar issue


Hello guys,
I have a tx5 pro connected to the TV via HDMI ARC cable to the HDMI 2 port. On the HDMI 1 port I have the soundbar. When the tx5 pro is switched on the TV is able to communicate with the soundbar and the sound is good. When the tx5 pro is switched off (standby) the TV can’t communicate with the soundbar (the display of the soundbar is switched on and the connection is blinking) so I can’t hear any sound from it but only from the integrated audio of the TV.
If I remove the power unit from the tx5 pro so there is no power or the HDMI cable the TV is able to use in the right way the soundbar.
Any idea? Is there some setting on Coreelec to avoid this issue?
Many thanks for any suggestion