TextTags not removed from tag table

["Gilzad Hamuni" <gilli4 gmx net>]

Hi list,

in order to keep my memory sane, I try to delete all text tags whenever I clear the text buffer of a text 
view (buffer.remove_all_tags(startIter, endIter)).
However, I get the warning that the tags I deleted are still in the tag table ("A tag named 'tag_1' is 
already in the tag table."). I searched the net but couldn't find any hints on what I could be doing wrong.

I've attached a vala-example of my approach to this mail.

Thanks in advance for any help.

gilzad