Thanks to David for his very helpful tip.
If you are using umlauts (ä, ö, ...) in your notes, some further replacements are helpfull, cause umlauts may appear "crippled" too.
As far as I found out until today, in the rtf file the following (wrong) unicode sequences (incl. trailing blanks) must be replaced with "" (string with length 0):
"\u1460 " (Unicode \'c4 / Ä)
"\u1492 " (Unicode \'e4 / ä)
"\u1522 " (Unicode \'d6 / Ö)
"\u1510 " (Unicode \'f6 / ö)
"\u63632 " (Unicode \'dc / Ü)
"\u63637 " (Unicode \'fc / ü)
"\u63635 " (Unicode \'df / ß)
Regards,
Daniel