While in linux, I wasn’t able to write a script, witch could find those special character files, this simple cmd.exe command for windows will write every broken file with the given character into a text file.
dir /b /s Z:\Folder\"*o’’*" > Z:\ös.txt
Mount the required directory.
Then go into a directory with a broken file.
cd Z:\Folder
The “dir” command will show you all files in the folder and also how the “Umlaute” looks like. You can copy & past them into the command.