This is not a complete answer.

You can't store "Unicode characters," you can only encode them into bits and bytes that can be stored.

You haven't said if your hash contains UTF-8, ISO8859-1, or some other encoding. The "é" is a character, but its representation is different in each encoding. If any part of the process does not handle the encoding or decoding correctly, it ends up with some other character, or it ends up as invalid and undecypherable bits.

If the database supports UTF-8 encoding, then talk in terms of UTF-8 encoded strings, not simply "Unicode characters."

You may also want to read my prior writeup, FMTYEWTK about Characters vs Bytes.