Using Traefik Reverse Proxy with Nextcloud and Docker OnlyOffice -- OnlyOffice tries to download document, doesn't happen with Nginx


So I have two test setups

Reverse Proxy (Nginx) —> Nextcloud —> Docker OnlyOffice Document Server
Reverse Proxy (Traefik) —> Nextcloud—> Docker OnlyOffice Document Server

Please note that both Reverse Proxies point to the exact same Nextcloud installation which points to the exact same OnlyOffice Installation — so essentially only the entrypoint is different between the two proxies – The backends are the same (not a copy – they point to the same server).

Nextcloud 20.0.2 with Docker OnlyOffice ie: Traefik 2.3.2 and 1.18

When using nginx everything seems to work as expected when selecting a .docx document within Nextcloud —> I get transferred to the OnlyOffice server and the document opens

With traefik, I select the document within Nextcloud and then the OnlyOffice document server opens but I receive this:

I have no idea when using Traefik it seems there is a notification to download the document. With nginx, I don’t get the prompt to download. Is there something with traefik that initiates this request?