Media files imported from AAF that contains special characters are imported with wrong characters, and therefore cannot be relinked.
The AAF import includes an option “Use UTF-8 conversion to import Links/Locators Path Names”.
This allows converting the referenced path names (called Locators in AAF/OMF) using UTF-8 coding.
If you have troubles to import some specific files that contains special characters, disable this option in the AAF import window.