We Currently use E.W.O.N Cosy 131 but I have been having issues with them dropping offline and needing to me power cycled at to different recent installs.
For what it's worth, I've discovered upon working with e.w.o.n support that this issue typically is because of electrical interference on the incoming WAN ethernet cable (or possibly LAN cables may cause the problem too)
The 131 is more susceptible to noise than the older models were. I've fixed up several sites that had long runs of ethernet cable on the WAN side. Changed this to shielded and the problem with the 131 going offline was solved.