Display bug? Shadows disappear when large curve is visible

I have a large circle (and some 2D blocks) around my drawing to easily locate the stuff, but when this is visible then the shadows disappear and the view gets a large “near clipping”:
(Project is situated close to W0,0,0)

With circle and blocks layer turned off:

And with circle and blocks just hidden:

(The ground isn’t recalculated when they are hidden, only if their layer is off)