I think to recover, you’ll have to manually docker rm/rmi the leftovers, then rebuild.
Quick overview of that:
docker images -a
# identify useless images (old discourse base, untagged), then
docker rmi d25ec275fb1d 818beea55263 cdb5237bc8a7
docker ps -a
# identify dead/defunct containers, then
docker rm 7f32e8715c89