I have run across lots of problems like Sandvine but  error: Offline (Metadata not supported) is a new one

Any serious client will have support for metadata transfers. Have you added blocklists found on this forum? I suspect it's a surveillance node. Less likely: it's one of the public DHT crawlers looking for metadata itself.
Try to write down the IPs you see with this error message, if you notice any pattern.

I figure more are using sandvine to block torrent connections etc. When I see connection reset by peer, I immediately suspect sandvine is involved.

By injecting connection reset it can block a torrent session between peers. I wonder if the reset component of the protocol needs to be checked and made more adaptive.