I have a documentType which includes a simple Boolean value. 

I main it using two user controls: one where default the value should be False, and another where the default value should be True. They implement the umbraco.editorControls.userControlGrapper.IUsercontrolDataEditor interface. A sample of the value logic is 

get

{

  return CheckBox1.Checked ? 1 : 0;

}

set

{

  if (value.ToString() == "" || value.ToString() == "1")

  {

    CheckBox1.Checked = true;

  }

  else

  {

    CheckBox1.Checked = false;

  }

}

These are then created as custom datatypes, using the Umbraco Usercontrol wrapper. 

Everything works fine, until I sort the content, at which point some of the content nodes have their property value reset to NULL. My user control isn’t called during the sort (no breakpoints trigger), so I think this seems to be a problem with the core behavior. However, I'd very warmly welcome any information that the bug lies with me!

(I use the following SQL to check what’s happening with my property.)

SELECT

         t.alias

       , pd.dataInt

       , pd.dataDate

       , pd.dataNvarchar

       , pd.dataNtext

       , n.text

       , n.level

FROM

       cmsPropertyData AS pd

       INNER JOIN umbracoNode AS n ON n.id = pd.contentNodeId

       INNER JOIN cmsDocument AS d ON n.id = d.nodeId

       INNER JOIN cmsPropertyType AS t ON t.id = pd.propertytypeid

WHERE

       d.newest = 1

       AND d.versionId = pd.versionId

       AND n.trashed = 0

       AND t.alias = 'myProperty'

;