While I'm not getting errors now, neither your Opus ExifTool Script nor the one by Polar Goose will find all files with IPTC Keywords - the only metadata field I've tested.
And the number of photos found varies by 1 to 3 files each time I test 'Find Files'.
I find more photos with IPTC Keywords by sorting by that field and waiting very patiently for the column to populate.
Some photos with IPTC Keywords are never found with 'Find Files', so I have tried to figure out what is different about those files, but I have not yet succeeded.
I can keep trying to figure out the difference if it would help you.
See this discussion: Find Results Inconsistent/Incomplete with Script Column