Same thing happened to me. Woke up, collected my guild rewards (gold keys, glory keys, souls,gems), then left the game. Came back, saw i had guild rewards again, so i collected them again. Fiddled with my troops a bit, then saw the mail icon up again, with more guild rewards. I tested it a bit more at that point to see if it was indeed a glitch, then I let my guild leader (Chy'tara) know, and she went through one of her contacts to inform the devs. I'm just hoping I don't get banned since I didn't know what was happening.