I think I would add in my opinion poor design, Other bikes I have owned the stator was not bathe in hot engine oil while producing it's own heat from making juice. Now I may be wrong but that's my thoughts.
Jerry
Oil will collect any metal particles from internal wear. These will be passed over the stator and may collect on it or the rotor and eventually assist in it shorting out. I'm thinking that oil even from a hot motor cools the stator a bit more than a dry stator would. Especially when in heavy use.
To add my half-brained opinion....since the stator runs at full charge all the time, and being shunted to ground, instead of being regulated on/off, that seems like that is what is killing them. Talk about creating some HEAT! yeeeesh..... :heat: