wp_read_image_metadata filter ignored?

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??

Start by reproducing thumbnail regeneration with the wp_read_image_metadata filter and compare its image_metadata with metadata produced during upload. Trace the regeneration entry point and confirm the filter is applied so regenerated thumbnails retain the added EXIF information.

Written by the indexing model from the issue text.