It might be something like your router or a VPN not allowing port forwarding, so although they can technically connect, they can't actually download anything from you.

I use mullvad vpn which doesnt allow port forwarding and I see the same (or something similar). I really need to set up a different vpn for torrenting so I stop being a massive leech.

Hmm strange. Maybe you should ask/crosspost this to a privacy community (if you haven't already), seeing as you are asking about this from a privacy perspective.