I'm also having similar issues if the device is not connected to the electricity grid. In particular, leaving the stylus near the screen (appr. 1 cm) while making a pause in taking notes would result in the screen not detecting the stylus any more if i don't lift it 5-6 cm away. If i clear the stylus away, afterwards responsiveness is restored . I also assume it is power management driver issue because as i said this is not occurring while the device is connected.
This issue doesn't seem to cause a lot of discomfort to other users though, since it's primarily me that is complaining all the time. Maybe people are mainly using the buttons or are not really taking notes extensively.