1.8.7 Errors in "Find similar files"

[rsbrux]

XnView: MP 1.8.7 - Windows 64 bit
OS: Windows 10 64bit

FInd similar files is unreliable when the option "Between folders only" is selected.

Effect: non-duplicates are erroneously marked as 100% identical, which can lead to their accidental deletion.

To reproduce:
1. Open this directory in XnView MP.
2. Click on "Tools" - "Find similar files".
3. Add this directory to the list of directories to be scanned.
4. Select "Similar image content".
5. Set similarity to 60%.
6. Ensure that "Between folders only" is selected.
7. Click "OK".
(see SimilarityTest0.jpg)

Actual behaviour (bug): XnView mistakenly identifies non-duplicates as duplicates.
This has been the case for a while now: at least since 1.8.6, but probably longer.
If one photo in a group of similar files is a 100% match, then remaining matches can still be labelled 100% matches, even when they differ from the original/reference photo. (see SimilarityTest5.jpg)
Sometimes images which do not meet the matching criteria are mistakenly listed as similar. (see SimilarityTest1.jpg)
This behavior seems to occur only when using the option "Between folders only".
If the same images are scanned from a common parent directory, XnView MP exhibits the expected and desired behavior.

Expected behaviour:
1. Radically different images should not appear in the duplicates list.
2. Slightly different images should not be marked 100% identical.

[xnview]

Thanks to your detailed description I can reproduce the problem.