When the rendering of tensor glyphs is activated for some 2D view ( i.e. Axial ) it gets redrawn each time the mouse pointer leaves the render window's area ( i.e. towards other renderwindows or the GUI ). It also happens when the mouse pointer leaves/enters the whole window of the application.

It is disturbing since the glyph rendering time can be counted in seconds. Moreover if not all displayed voxel have a glyph to render because the max number of glyphs is exceeded, the distribution of the rendered glyphs vary on each redraw.