I've figured out what happens.
I charge it all night. And I usually keep it right next to my bed and I wake up sometimes a little early to see what time it is And from that moment on it stops charging. I've tested it a few times over the past few days.
It's no big deal to me. As soon as I wake up for real I just unplug and plug again while I shower.
Can you guys try it. It only happens after being at 100% for many hours.