The charging system issue on the 2009 MDX flashes briefly and then disappears. Even after replacing the alternator, the problem persists. While driving, the charge level decreases and then recovers. It's really frustrating, is there any expert out there?

Years ago, when I was riding a CBR400, I encountered a similar issue. After checking, I found that it was a faulty regulator module. The engine generates power which then goes through the regulator before charging the battery; otherwise, high current and voltage can damage the wiring and battery. Hope this helps you.