I have a new c510w camera. And there is a problem with tilt operation in manual, patrol or motion following mode.

After camera is moving upwards or downwards and no matter which way you choose to do it, it's always return a bit lower to the start point. Is it encoder problem or firmware bugs? And how to solve it?

(By the way, everything is ok if I make, for a example, 2-3 viewpoints and start patrol in pan mode only)