Question: can this 3d plot be better?

with(plots):
plot3d(sqrt(25-x^2-y^2),x=-6..6,y=-6..6,axes=box)

Notice it doesn't completely go down to the x-axis. 

It can be partially fixed with this

plot3d(sqrt(25-x^2-y^2),x=-6..6,y=-sqrt(25-x^2)..sqrt(25-x^2),axes=box)

but due to bugs in earlier versions of maple I can only achieve this

The missing area in the positive side y area has been fixed in newer versions of maple, however the jagged areas in the negative side are still there.  If I use 1 + sqrt(25-x^2-y^2) instead it is okay in newer versions of maple (that is the fixed missing area in + y and the jagged areas) it graphs the semi sphere.

Even -1+sqrt(25-x^2-y^2) works.  So something is happening when the graph is trying to be drawn at z=0.  Any ideas?  workarounds?  is it a bug?