I hope this is the right place for this type of advice. I have a cheap A4 tablet, and have been having problems recently with the pen starting to miss lines. The cursor was still tracking my pen and the buttons worked. It turned out the fault was the battery connection inside the pen had fractured the solder connection.
If anyone with a Trust, or Aiptek type tablet suffers the same fault, its an easy fix to have the contact re soldered, and restore full operation of the pen and tablet. Don't scrap your tablet for the sake of a faulty pen.