As a guess, your TV is re-establishing the ARC or eARC connection to the Sonos, something Sonos has no control over. It may be valuable to check the TV for software updates, but I would hold out much hope that Sonos will be able to fix this, they’re just a client of the hub which is the TV set. 

My tv is a newer one Philips Oled. it is full up to date.

Then you’ll need to wait for someone at Sonos to look at your diagnostic. Or, the more likely solution, contact someone at Phillips, since this issue appear to be with your TV, and not the Sonos Arc.