Hi @Hans De Cuyper 

Welcome to the Sonos Community!

I very much doubt this has got anything to do with you watching TV. Alarms will play a chime when the speaker with the alarm set is unable to reach the source of music selected, at the set time. Please switch your WiFi router off at the power for at least 30 seconds. While waiting, please unplug your Bedroom and Bathroom Sonos speakers too. Turn the router back on, and when WiFi is back a few minutes later, turn on the Sonos speakers again. If you have any WiFi boosters or extenders, these could be the problem - once the rebooted Sonos speakers have solid white lights, turn any boosters/extenders you have off and on again.

If this doesn’t help, and you do have boosters/extenders, please turn them off until you can test again.

Still not working? I recommend you get in touch with our technical support team, who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it says is happening.

Thank you, Corry.  I also thought that my netwerk was not stable enough to reach the bedroom, so I ordered a Sonos Boost.  It happens less now, but it still does sometimes, and every time with other speakers in the house.

My internal WiFi also has boosters but I have them all on 5 GHz, so they stay away from the Sonos Channel that I have set. 

The network seems stable enough, because once the music plays I never get an interruption with the radio channel...

Just one more info...there are three boxes that start up independently at the same time with an alarm setting.  I cannot group them into one in the alarm setting, right?  Otherwise, that might help maybe....

Good thinking! That could be it. You can set one alarm to play to a group, but the alarm won’t create the group. Go into your morning alarm entry in the app, tap on Rooms and make sure Include Grouped Rooms is on. As long as your 3 rooms are grouped when you go to bed, they’ll all play the alarm. Remove all but one morning alarm, so there’s just one for the group. I recommend you make the group by selecting the speaker that has the alarm first, then grouping the other two to it. This should be the speaker of the group with the best connection - probably the one closest to your Boost. This will minimise the possibility of excess network traffic across the group.