Yeah not entirely sure this can be blamed on eleaf, if you changed the settings. It sounds to me like the button is getting stuck, somehow, have you tried cleaning it and behind it as much as you can? Also, I suppose you could warranty it. I've found eleaf's stuff to be reliable. I mean I get it, I am not a pico fan, but it wasn't really the mod's fault I didn't love it, and I've loved plenty of other eleaf stuff....
Hope you can get it sorted out one way or another though....
Anna