Ahead of our 3000 mile US West-Coast trip my son and I bought a S20 dual set. One week later the casing of my son's module already let loose. Two days before leaving Europe we got a replacement from our dealer. Everything seems to be working fine: sound, commands, pairing etc. On the 3rd day of our trip the intercom sound level of my son's words dropped till a far away whispering, while my son could hear me perfectly. Also did my son's Sena not react any more to his commands. We tried everything: factory resets, new pairings, even fault reset but nothing helped. Eventually my son's words didn't come through anymore. After consulting our dealer back home, we switched modules. His module seemed to be working fine on my baseplate: his module reacted on commands again. Default part was either his microphone or baseplate (or both). We also consulted Sena Netherlands who gave us the number of Sena USA.  We tried a couple of times to reach SENA USA, but every time long enough on hold to reach the answering machine. They however never took the opportunity to reach back to us. Also tried to persuade a number of Sena dealers in US to help us out, but they all were reluctant pointing out Sena's warranty rules: either directly via Sena or the original selling dealer, which weren't options for us of course at that time. Two times during our 3 week trip we were surprised by getting my son's volume back while we hadn't changed anything! But only for a couple of hours. After that total silence again. 

Today my son is gong to exchange his set for a new one that will hopefuly last longer than the former two.

Sena: overall quite disappointing this experience regarding both the quality of the S20 and your US customer service.