Got a 2014 Sandstorm couple months ago have been out 4 times now, and 3 times the tankless hot water failed to work. We have been taking "cold" showers, which isn't so bad here in So Cal during the summer :) The trailer is in the shop right now for this problem, they said they found a bad switch in the unit and have to order new one. I'll find out exactly what switch and report back later this week. The problem I had was the fan would come on, but the propane heater never fired so it did not get hot and fan shut off after about 15 sec.
Reading these forums looks like these tankless units have some reliability problems. Hopefully mine will be ok once fixed. I have tankless unit in my house and works great for the family, unlimited piping hot water, which is why I went for this upgrade on the toy hauler.