When I first got my Vision it did this. The AP worked great on the first few test flights. Then I tired it on my first Cross Country. Since I was going to be going a long way I put in a higher altitude and climb rate. At around 3,000 ft it abruptly pinched down. This happened several times before I abandoned using it. After some on-the-phone troubleshooting with TT (Great people, and great support!). The sent me a new one and I returned mine. No problems with the new one, so I called to find out what they found. - It was a pinched tube internal that lead the AP to think I was approaching stall speed when I was not.