Hello Ondra,
i've created a video ---- usually the viewport is quite smooth... when using the mouse. After i opened the material-editor or rendered an image - the navigations withing the viewports is horrible. You kinda get that impression at the end of the video, where i didnt released the mousebutton during moving or rotation. It seems stuttering and the object jumps to a certain position where the mouse is...
Working with the scene is quite impossible.
I've seen that in different scenes lately, but hadn't found the time to figure out the reason for that. I didn't had this behavior when using vray-as render engine or merging a affected scene into a new scene - so i'm not sure if there is that original scene corrupted or if that scene got degraded over time.
I couldnt see the effect in that merged scene.