What are the resolutions of the video, and the HDRI image? To confirm, if you render a photo, there will be no issue on the HDRI, and the problem occurred only to rendering videos?
We will compress HDRI to 2k when in preview mode, but it will not influence the final render, so we may need your files to test and troubleshoot.
Besides, do you use a render queue? If yes, please render the video solo, then see the result.
If the problem remains, please send me the HDRI image for testing, and it would be good if you could send me the scene file as well. My email is firstname.lastname@example.org