We read metadata for .mov files using ImageMetadataReader.readMetadata(File);
To accelerate the process, we use multiple threads, however, this causes Metadata-extractor to sometimes swap the metadata between two files. It's pretty rare when I test, but I have a customer who can trigger it repeatedly. I assume that the Metadata-extractor movie reader simply isn't thread safe. Wrapping the readMetadata call in a synchronized block makes it work, but with a significant time penalty.
(The same logic also reads metadata for images just fine so it's safe to say that the client code is fine)