wp_read_image_metadata filter ignored?

[mmjaeger]

Hello - I'm using the "wp_read_image_metadata" filter to add some additional exif information to the image_metadata - works just fine on uploading pictures - however, when using regenerate-thumbnails the filter seems to be ignored and I end up with the default image_metadata information - when using a different plugin to regenerate the thumbnails it works fine - wonder what the issue is and how it can be fixed??