As well as the speakers you need the app to not auto-update. If one updates, the others do too so that the release versions stay in sync. 

As I thought is that the update refere to the system, not the speaker.

Using the app, go to Settings, System and scroll down to System Updates. That sets for the speakers themselves but not the app. You then need to turn off automatic App Updates on your phone (and Mac/tablet/pc if appropriate). 

Ok, thanks

Thanks, I have made so. Then I manually let all other apps to update. Now I have Sonos 15.3 and will have so for the rest. I found it on the net.

Note that some updates related to Sonos and other products/services, may get released to address network security vulnerabilities, aswell as any new features - so be mindful that you maybe leaving your setup open to those things if you do not keep the software/firmware up-to-date. Just to remind you of the consequences. perhaps, if you choose to not keep those things updated.

All other apps will I let be updated manually. If there will be a problem in the future with Sonos 15.3 I can update it to latest version. Then go back to 15.3. If there still is a problem, I have to accept the missing of playing internal music.