sanitize_key filter and Hebrew

In my plugin I have an associative array whose keys are defined partially by the user and their input into a form. It’s crucial that it stays this way because sometimes the user wants to override a value for that key and sometimes they don’t.

So far it’s been working fine. I use the ‘sanitize_key’ function to ensure that the associated key is a valid string, but it’s been brought to my attention that when the user input is in hebrew, only value appears in the array. This doesn’t happen for any other special character language like Chinese and Japanese. It would seem that the filter returns the exact same alpha-numeric value for every word in Hebrew. Has anyone else run into this? Is there another function/filter I should be using instead?

I appreciate any advice anyone has. I’ve been hitting my head on this one for days now.