A usual UTF-8 code for ä is “C3 A4”, in your document it is “61 CC 88” which is actually a separate definition for a and diacritical marks (umlaut dots) to be rendered as a single glyph.

I have found an explanation by the link http://www.redleopard.com/2008/12/character-codes-and-encoding/

Unfortunately PD4ML does not support that notation for the time being. So the only workaround is to replace “61 CC 88” byte chains with “C3 A4” or tune your database to return UNICODE data as regular UTF-8