Stream recording titles

I have around 30 recordings uploaded to Stream, all of which also have an uploaded thumbnail as Stream has an irritating default of picking a random section from the recording. 

Those recordings are embedded (via copy/paste of the URL) into our modern Sharepoint site and, 

since Monday the thumbnails are sitting "on top" of the recording, obscuring the previously visible title

All the recordings have been removed and reuploaded without changing anything

Can anyone explain what has changed as my previously beautiful site now looks a mess