I have had trouble with the Error 26 in the past. After a crash, my Phantom would not calibrate well. On takeoff it just fell over. After several Advanced Cals, I started gettig error 26, and then one day it just started flying perfectly. I have flow at least 20 flights and have had not problem, however, error 26 continued to show. Just today, I upgraded the Assistant Software to 2.1 (from 2.02). Error 26 nolonger appears and I am still flying well.