Adobe Pro DC - Marking Fields as Read-Only After Digitally Signing Issues

I am creating a PDF form that contains 4 digital signatures.  I am selecting a signatures and am in the property options for that specific signature looking at the "Signed" tab.  I select, Mark as read only, than choose "Just these Fields.

When I select "pick" a new box opens that lists all the fields in my form with a check box next to each.  It appears that I can select the fields I want to mark as read only, however, when I attempt to check a box, nothing.  I can select "select all" and all the fields become checked, but I cannot check individual fields.

I am using Adobe Acrobat Pro DC - 2015 Release (Continuous) | Version 2015.017.20050.

This issue was noted by thomashowardjr Aug 8, 2013 11:11 AM; I can't see where it was ever answered.  I am experiencing same issue with Adobe DC Pro.