I updated the container (image) yesterday and suffered the same issue. I only now realized that Collabora swiched the SERVICE name from loolwsd to coolwsd including /etc/coolwsd path – and also all corresponding URLs, as well as loleaflet to browser. After changing all these in my NGINX reverse proxy configs, all was back to normal.
I only now realized that Lymkwi already wrote about that 3 weeks ago.