The problem is most likely you are using layers.  Say you have the base layer and one other.  If most of your camera movements were mad on the Base layer and then you switched to the other layer and made a camera movement, it is going to override the lower levels movements and you get the camera jumping all over the place.  Best thing in the world is to ignore the layers feature and only work on the base layer. Highly unlikely this will ever be fixed. 

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13