Replacing text through multiple files replaces the wrong text when a line contains umlauts

When I have the following text in a .cpp-file:

"ä" + abcdefgh;
"äö" + abcdefgh;
"äöü" + abcdefgh;
"" + abcdefgh;

... and want to replace "abc" with "123" via the advanced search/replace I get the following output:

"ä" + a123efgh;
"äö" + ab123fgh;
"äöü" + abc123gh;
"" + 123defgh;

This does not happen when the file is already open in an editor.
All files are UTF-8 encoded and the text editor is set to use the system encoding (UTF-8 under Linux).
The encoding for the project has to be set to latin1 and the editor settings for the project have to be set to "Global".