Photoshop: Character Encoding of Keywords

OS: Windows 10

Photoshop Version: CC 19.1.2

I guess there is a character encoding problem with Photoshop.

This is what I'm doing:

     -I open an existing JPG File with Photoshop which has no keywords

     -I open the panel "fileinformation" and navigate to the tab "simple"

     -I enter the text "nöice" with a german umlaut into the field "Keywords"

     -I save the changes of the file in photoshop

Examining the file with exiftool (or similar programs) I see that the "Keywords" added in Photoshop are

saved in the attribute "Keywords" and "Subject", but with different encodings.

Further examining those strings I get the following results for the original keyword "nöice":

Subject:

     byte sequence: 6E.C3.B6.69.63.65

     ->correct UTF8 encoding

Keywords:

     byte sequence: 6E.C3.83.C2.B6.69.63.65

     ->seems like the string was two times UTF8 encoded and is therefore malformed

When I instead create a new file in Photoshop, add the keyword "nöice" and save the file as a JPG,

everything works fine:

Subject:

     byte sequence: 6E.C3.B6.69.63.65

Keywords:

     byte sequence: 6E.C3.B6.69.63.65