NX Duplicate sheet letters and zone numbers displayed after deleting Drafting sheet.

After deleting a drafting sheet, the existing sheet shows duplicate sheet letters and zone numbers. Why?

The problem is arising because Create Labels toggle in the Borders and Zones command is checked in the template file. When this setting is turned ON, the zone notations can get recreated during an update event, most likely triggered by sheet delete edit in this case. The problem is seen when the recreated zone notations get mixed up with the ones created by user.

Unchecking Create Labels toggle should rectify the problem.