It might be one of those odd features which date back to the 60's where cars would leave their lights on for 30 secs so you can find your house at night if you left the lights in a particular setting or left the stalk down. I would not buy another stalk as they probably all do it. At JUnctions, when it stops indicating, just cancel and re indicate. A main dealer might help you or if you have the original handbook these features are often explained in laborious detail so it should tell you whether it is actually faulty or not.
Mike
May 2010