IThe mechanism is rather reliable, though sometimes, by unknown reasons, it
gets stuck. Open the serial port lid, take some thin object, like a knife of a thin flat
screwdriver, put it to the split above the serial port connector and gently widen
the split, i.e. separate the upper and lower parts of the case a little, giving the pen
holding mechanism more volume so it could release the pen, simultaneously try to remove
the pen pressing on it until the click.
IThe mechanism is rather reliable, though sometimes, by unknown reasons, it
gets stuck. Open the serial port lid, take some thin object, like a knife of a thin flat
screwdriver, put it to the split above the serial port connector and gently widen
the split, i.e. separate the upper and lower parts of the case a little, giving the pen
holding mechanism more volume so it could release the pen, simultaneously try to remove
the pen pressing on it until the click.