Webdav 502 Bad Gateway after upgrade to Seafile 12

Hey there, I upgraded my docker seafile from 11 to 12 (including caddy) and after some hiccups (ex. the CSRF thing) everything seem to work… except Webdav. I get a 502 Bad Gateway no matter what I change. I already changed the proxy_set_header in the nginx conf. but that doesnt work.
Is there anything else to change or have a look into?

Is there anything else to change or have a look into?

Log files, perhaps?