Hi folks.
Another possibility of jitter that is often overlooked is when the model is very far from the origin. Open GL has a hard time with that.
But, you will notice that during the modeling phase since the jitter effect would manifests itself when orbitting, panning and zooming.
To see this effect, try this:
1 - Draw a cube near the origin.
2 - Move it 100 km (100000 m) along the red axis.
3 - Use Zoom Extend to find it.
4 - Orbit to see a bit of jitter.
5 - Move it another 100 km. The jitter increase.
Just ideas.