[NTG-context] Disappearing Columnar Text

Hi, When using "\startmixedcolumns[balance=yes,grid=strut]", how would you put a 0.5em vertical space between a subtitle and a list of items? The following code gives a simple example: http://pastebin.com/raw.php?i=pT5tcXfc Uncommenting the following line hides the list items under "Subtitle A": %after={\vskip-0.5em}, See: http://i.imgur.com/wFIkRZY.png Removing a list item from the end of the list for "Subtitle C" makes the items appear again. For example, change the last "\dorecurse" macro to: \dorecurse{7}{ \item {a list item} } How can I tweak the amount of space between a title before a list while using a two-column layout without causing the content to disappear? For reference: http://i.imgur.com/2EysUWp.png Thank you!