Another problem with the contour tool

Hi,

I've come across yet another problem with the contour tool. In some circumstances it ignores subpaths when generating the contours.

Original without contours (see attachment):

 

Same shape after applying a 3 mm inside contour. Looks just fine.

 

But if I instead use a 3.5 mm inner contour, the innermost subpath is ignored and does not get outlined:

Fill shape posted.cdr