Did you check all the grounds. Sounds like an intermittent connection.

 

check again for loose connections or a chafed wire.

 

Had a similar problem on my '08 RG, regulator was bad.

 

That is exactly how the voltage regulator fails. Intermittent at first then a hard failure.

 

+ 1 on the Regulator. I have the same issue. Occasionally start the bike and not charging...a rap on the regulator with a wrench and it will start charging.

 

If you don't test it when it's showing low voltage then everything will test fine. That's what makes intermittent faults so hard to find.
To answer your question, it can be either the voltage regulator or the stator.
My voltage regulator failed giving me an overvoltage but at the same time I'd get a very occasional low voltage code. Had the regulator replaced and now I don't get overvoltage. I do still get an under voltage every couple months or so that goes away pretty quickly. I'm sure at some point it will get worse and I'll have to replace the stator. In the mean time I watch the guage and smell the primary fluid occasionally.

 

yup, had to change mine out on a 12 RG..whenever it would warm up outside it would drop voltage..when cold it would recharge the batt.