Grantourismo

I have a 2005 a3 8P with a 2.0 ltr BLR engine and Tiptronic transmission. The transmission began to play up. Firstly the key would not come out of the ignition after selecting park. The the auto transmission would not work, only the Tiptronic side. Then the selector illumination started time flicker. I removed the gaitor and found a small magnet stuck to the selector circuit board. I removed the magnet and the transmission works okay in auto but not the Tiptronic, the key comes out okay now but the selector illumination does not get brighter to show which position it is in. The circuit board has a black mark where the magnet has shorted out. Does anyone know where the small magnet may have come from? It is approximately 12 mm x 7mm x 3mm in size. Also how hard is it to remove the circuit board for repair or replacement?