Impossible to move along z with Grid Snap

I’m using Rhino wip and when I try to draw a box in the perspective view I cannot move the third point in z direction. The same happens when I use the gumball in z direction. This trouble appears only if the Grid Snap is active.
Is there something lock? (2.5 MB)

Yeah, looks like it’s broken. It happens if Ortho and Grid Snap are both selected. It’s now fixed in the source, and should be in a near future WIP. Right now you can turn off Ortho or press Shift to temporarily disable Ortho to get it to work.