Sorry about that bas.
I'm quite sure this is a Traktor issue. I've ruled it out in MP3Tag and iTunes - so, yes, it looks like it lies with Traktor.
Bit of a pain, that is. So now I'm looking for a way (I asked in this thread: Remove Trailing Special Characters apologies Florian if this has made extra work for you!) if there's a way to remove all accented/special/foreign characters across all tags and filename. Maybe an %ALL% action?