Exploring recently installed v2021, have found 'files with problems' on the dashboard, showing 12 problem files. Metadata write-back does not resolve these. The little yellow warning says check ExifTool output when attempting to write-back. It is so long since I used this, I have forgotten how! :-\ I cannot find this in help - so please help - thanks.
Just open the Output Panel (https://www.photools.com/help/imatch/#panel_output.htm) ;)
Doh! thanks