I have the same problem sometimes. I have excellent tracking points and when i select analyze forward the tracker goes crazy and does not always stay on point. On occasion i have had to reset and retrack 5,6,7 times before it actually stays in position, and the funny thing is when i get it working properly the adjustments i make are very small. i think its down to the video footage, if its not very clear or the track point colour is very similer to the background it gets confused.