Search on a word don't work, but if I add a separate single letter, it's ok...

Hello

It's not easy to configure, and sometimes I don't have any idea about how to fix a problem with Solr

On my website www.1819.be you can search on the word :

Exonération test

you will not have any result

If you try with

Exonération d test

it works, all titles with "exonération" are shown

did you already have this kind of problem ?