The English covers have just been replaced by German ones.
When I opened the folder with the movies again, the covers suddenly flipped and were replaced by the right ones.
So the problem solved itself.
Before that I looked at themoviedb.org and picked out the one movie I could remember for sure that it has an English cover.
There is also a German version at TMDB.
After the covers were flipped in infuse, this one and almost all others were in German again.
Thanks a lot anyway!
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