I am not sure if this is only on H5P.org but I got it here, using Chrome. I checked it on Firefox it works fine
When you refresh the page or select hub again it loads normally.
Issue happens on Chrome - in Moodle and WordPress as well, below are the screenshots
Should be fixed in relation to
The hub always loads entirely
Do not rely on timeouts (e.g. postponedResize()), instead make sure that everything is properly loaded before resizing iFrame