Using S3 storage // Large Uploads

I’ve tried uploading directly to my S3 bucket, which works, but for some reason if I don’t do the upload directly through the Nextcloud interface, Nextcloud freaks out and becomes unusable. So I tried uploading using the Webdav connection, but its incredibly slow.

I do have encryption disabled.

Any other options for doing VERY LARGE uploads to S3? And by large, I mean about 10Tb.