Possibly due to c13cde24cc
This commit clamps the `brush->size` value to 1 at lowest for the
Grease Pencil Draw mode. There are situations where when the brush scene
space value is set to a small enough size that the distance calculated
by `project_brush_radius` becomes 0.
When this value is set as the actual brush size, the `wm.radial_control`
operator fails to work properly as the new size is now lower than the
expected minimum value, causing incorrect clamping of the modal value.
Pull Request: https://projects.blender.org/blender/blender/pulls/129937