I had several times this problem. The horizon was out of level. The Movi was correctly balanced. With a fresh battery. I was in the back of a van shotting a car following us. We were speedy making turns. After a while a noticed that the horizon was out of level ( roll axis). Next I was in the side of the van, shotting the car in parallel. The direction of the car and van was straight. After a while the horizon was out of level ( roll axis). We stopped and the Movi didn´t get it leveled position. I had to force the roll axis to get the horizon leveled. When you start up the Movi the roll is OK, leveled. This only happend when we are in motion with speed. I atached a picture of other situation that I was riding a Segway. The horizon out of level is clear. From the web of Freefly: "The control algorithms developed for the MōVI utilize a very high accuracy GPS. This GPS allows for acceleration correction when the gimbal is used outdoors and has a GPS signal. This feature is useful when used on cars and helicopters where sustained extreme accelerational forces can cause non-GPS aided systems to drift.I assume that this horizon driffting it happens for the aceleration and the speed of the vehicle." Why does it happen?