Find Similar Files Broken

[Strobe]

Just installed 2.31, and Find Similar Files (Similar Picture Content) seems to be broken when you use it on a folder - I have several folders with several 'obvious' similar files (even same resolution) and it is not finding them, even if I reduce the "Similarity" setting to a very low value.
eg. if I reduce "Similarty" to "1" - which would normally find many, many files, I get "No files found", let alone "90" or so which I normally use to de-duplicate doesn't find any.
I've tried turning on/off the new "Use extension" setting but that made no difference.

Thanks.

[xnview]

yes a known issue