Oh, I thought we are talking about custom post type contents, in this case the index table won't help, as the taxonomy term tables don't need indexing.
I actually thought that taxonomy terms are stored with sanitation, it doesn't make sense, but I guess today I learned something new. I might have come up with a possible solution, without touching the plugin code. Try putting this into the functions.php file in your active theme directory:
This will try to detect differences in sanitised / unsanitised inputs and appends a new search phrase if finds anything.Best,
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