Cold start up of the AFS5600 with 3500 2nd screen, the altitude data reads 43,700 ft for about the first 15 minutes. It then slowly gets real for another 5 minutes until reading correctly. Data is going to the G330 transponder which shows pressure altitude of 43700 when enabled. Seems to be temperature related as it corrects itself after about 15 minutes of flight. Need help please.