I fried one of my mini boards by putting 5V to the 3.3V pin by accident.
Well, it killed the LDO which now gets burning hot powered from USB and it applies 5V to the ESP chip, instead of 3.3V
The point why I am writing this here. The ESP works fine. However, it gets hot and possibly will receive damage by the over-voltage.
Thus, it might be indeed a defect of the LDO.