Steps to reproduce the issue

In the Finder indexing plugin, I set multiple values for one taxonomy as following:

$item->addTaxonomy('Variants', 'catalan');
$item->addTaxonomy('Variants', 'occitan');
$item->addTaxonomy('Variants', 'test');

Expected result

On the search page, the item must be returned on search results if I filter by Variants field with any its variants.

Actual result

Some items are missing on search results.

For more details:
If I filter by Variant "occitan",
The results total (in pagination) display correct number of items (E.g: 1-14 of 14)
But the search results displays only 6 items.

System information (as much as possible)

After some investigating, I can fix this issue with solution below:

1. Open the file:
   components/com_finder/models/search.php

2. Go to the code line 226:
   ->select('l.link_id')

3. Replace it with below one:
   ->select('DISTINCT l.link_id')

4. Save changes and the search filter works worked correctly.

Additional comments

I hope that you can apply this fix on next release of Joomla.
Thanks