We have a product named "İncir". İ is turkish char. When we search for any word Grandnode compares the word written from the search panel with the word in mongodb. Grandnode comparing strings case insensitive. In Grand.Services/Queries/Handlers/Catalog/GetSearchProductsQueryHandler.cs file
In the mentioned line there should be ToLowerInVariant() instead of ToLower(). You can fix it in your project, we will introduce fixes in the next version of GrandNode.