In the current version, every time you save an existing namespace your namespace BB-Codes are reverted to their defaults and the buttons are cleared.
In vault/special_dm_namespace.php, look for $tag_missing = false; and $tag_missing = true; and change them both to their opposites.
If you need to re-enter some of them because of this bug, all the buttons should be in the vault/images folder. If you had made any other changes to the BB-Code settins (i.e. turning off the option code for your help tag, or something), you may need to make these changes again.