S3 Error 500 when displaying video

I have a client site that has been working fine but as traffic has picked up we've noticed some seemingly intermittent errors relating to thumbnails stored on S3. We dont have a series of steps to recreate, but every so often when hopping between pages an admin message will appear saying 'S3 error 500' but the thumbnail and video will display ok.

500 suggests server error, but im not getting any luck working out where it is, was wondering if this was a problem for anyone else?