Hello
If there is not enough space to cut the wanted radius, you only get the "top" of the radius.
ex: Stock surface = 0 ; target depth = -5, only the first 5mm of the radius are cut = yellow toolpaths
SS = 0 ; TD = -10, there is enough space to cut the whole 10mm radius and you get the yellow + blue toolpaths
note: the toolpath are generated for a tool of 0mm diameter, so I can see the exact shape without the tool radius compensation. (do not forget to change for the right tool diameter before to generate the Gcode

)
to do the half bottom of the radius, as on the bottom picture, you must use 3D mop ...
++
David