I had for a long time an issue with sound explosions on my sonos speakers. Volume would go instantly to 100%. Others had the same experience. It is discussed in the support forum, but the cases are closed there, so I cannot report.
The solution seems to be to use Airplay instead of the Sonos protocol. I switched and no more explosions! The only downside is an old loudspeaker without airplay support that I had to replace.