The issue will be with encodings. If your columns are defined without the ‘n’ or “national” prefix e.g. nVarChar then the encoding of the string is Windows ANSI and you’ll need to define the encoding and convert it to UTF8. This also applies with the ‘n’ prefix you’ll need to define the encoding that was used to insert the data and then convert it to UTF8.
I have shared an extension method at https://forum.xojo.com/t/mssqlstringvalue-extension-method/68251 which will help with the Windows ANSI columns.