Empty subfolders or access denied when WebDAV is behind https via HAProxy

[mcsilver]

I have a docker container for bytemark/webdav and I can map a Windows network drive to it, provided I use http. As soon as I use https, it only works via a web browser. After mapping a Windows network drive via the https version of the URL, it shows me the immediate directory contents, but then either gives me access denied or empty contents for all subfolders.

My HAProxy terminates the port 443 traffic, forwarding port 80 traffic to the WebDAV container.

Is there something I must configure, either for the container itself or at the HAProxy config?

Thanks for any advice!