[resolved] Docker localhost issue

Resolved: proxy was broken on ipv6, updated my reverse proxy to connect directly to
I’m currently experiencing an issue with docker while running a container on a server.
Running on Debian 11, docker 20.10.5+dfsg1.
I was running Vaultwarden (a Bitwarden server) previously, but a day or two ago it stopped responding to requests from localhost on the assigned port.
The container was initially started with:

docker run -d \
  --name vaultwarden \
  --restart unless-stopped \
  -v /var/lib/vaultwarden/:/data/ \
  -p 8880:80 \

Right now, when I curl localhost:8880 I get the error “curl: (56) Recv failure: Connection reset by peer
However, when I curl (the IP address of the container) I get the data of the login page as expected.
This is the only container experiencing this issue, all other containers respond to localhost as expected.
What could be causing this issue, and how could I try to resolve it?
I have tried restarting docker, re-running the container, and changing the host port.