GREAT description! Mine was doing that all last year, but only once in a while on the open road just like yours. I found one of two issues right away, the battery terminal could not be tightened up all the way, leaving the clamp a little loose because of the aftermarket battery I had purchased right before the problem started. Then, I realized all my electrical issues had started with this battery change-out (alternator failure, radio c/b and starter failure), so I spoke with an expert and he mentioned he'd seen this before, and I should go out and spend the money on an OEM battery.
Well guess what, IT WORKED! and the bike hasn't pharted once since, and has no more issues, it has never run better. The Mechanic said he fixes many bikes this way!!! I threw away the "batteries plus" brand battery (only 8 months old), and all is well now.
With the alt being replaced and the Magna Power battery testing bad i went with a brand new Yuasa battery!!

Soon as my S S check shows up i gots a battery and a tire to get totally checked out.

RIDE SAFE.