system.tag.removeTag doesn't remove tag

Hello All,
I am trying to remove a UDT tag via script after copying the data from the original tag and copying to the new tag. New tag is added correctly, but system.tag.removeTag doesn’t remove the original tag. Path is valid. The except portion never fires.

code snippet below:

path = ‘[default]%s’%(event.source.parent.Ticket)

system.gui.errorBox(" Failed to delete tag %s",path)