Several Asian imports have shown up at my door with similar problems and it appeared to be the integrated voltage regulator causing the problem. Unlike long ago when the idiot charge indicator light was directly involved with the charging system some of the current alternators have a sender circuit and a charging drop out circuit that can cause a lot of grief. Bench testers don’t check those circuits and rebuilders seem to reuse faulty regulators because they function perfectly in the charge mode. Somewhere out there in youtube there is a video of someone who explains how to disconnect and bypass the failing circuits and keep the charging system operating well without them.