Aukey EP-N5 left bud not charging / lose connection

i recently bought the EP-N5 - have them now 1 Week. First all was okay pairing worked fine all cool.
but since today, the left bud gives up after 5 Minutes of using only right bud stays connected and powered. i did re-pair them and charged them both again to “full” but left bud stays almost empty.

how to RMA ? bought them from Amazon but their support sux.