If you right click on the build platform box it snaps the angle of the box just as it pleases. When the box is upside down (to work on the support points right clicking on the box makes it snap over incorrectly. I get around all this nonsense by navigating only using my SpaceMouse. the normal mouse is a total pain for navigation.
I worked out what the problem is - The mouse position is not updated if the SpaceMouse moves the box banking across the left and right of the screen. Imagine you are looking at the screen as if standing behind an aircraft (tipping the wings up or down using the SpaceMouse confuses the normal mouse.- (The box snaps back to an old position or a default flat position) - All other actions are fine (tipping forward and back, yawing left n right, panning and zooming are fine)