PS: also look at Plugins > XML Tool > About XML Tools, and include your version of XML Tools. Also go to ? > Debug Info > Copy debug information to clipboard and paste in your reply. These will let us know the particulars of which Notepad++ and XML Tools, so we can try to better replicate your circumstances.
Update Feb 25, 2020: issue #11 has been closed; the problem is fixed as of XML Tools v3.0.3.2