"failed to create locked file" when starting josh via docker

[RalfJung]

When I run this

docker run -it -p 8000:8000 -e JOSH_REMOTE=https://github.com -e JOSH_EXTRA_OPTS=--no-background -v josh-vol:/data/git joshproject/josh-proxy:latest

I get an error

2022-12-21T16:30:26.478227Z DEBUG josh_proxy: init mirror repo: "/data/git/mirror"
2022-12-21T16:30:26.530051Z ERROR josh: item=Error { code: -1, klass: 2, message: "failed to create locked file '/data/git/mirror/config.lock': Permission denied" } error=true

The /data folder exists because it was created by an earlier version of josh. I did a docker pull joshproject/josh-proxy:latest and then I started getting this error.

After some fighting with docker I managed to get it to delete that volume, and now things seem to work again. But still, that should not happen, right?