Out of warranty, hey? Reads to me like your shop knows what the problem is, from experience. Still, keep it simple at first? Check you got no chafing happening in wiring loom... flywheel to battery. KAWA regulators are solid state so intermitant is unlikely, it either works or it don't. If all checks out, pull the flywheel and check the leads offn stator coils for tight. That's what the shop would be pointing to. Whatever the fault it will be interesting when you do find it. Be assured you wont be the only one, neither
KK