Deleting Attachments on Sales Orders

I’m on ERP10.1.400.38 and am trying to delete Attachments from Sales Orders.

On Sales Orders where there are multiple Attachments I’m able to delete all but 1 of the Attachments. On Sales Orders where there is only one Attachment, I cannot delete it at all. 

I have right clicked on the Attachment in the ‘tree’ and selected ‘Remove’ and saved the order. I have gone to the Attachments tab, selected the Attachment and clicked the Delete button. Then saved the order. 

Nothing deletes the Attachment.  Is it just me? What am I doing wrong?

Karen