Software Flow Offloading and Port forwarding/upnp (plex)

hello all,

Longtime lurker and user of openwrt. I have a question about software flow offloading in combination with port forwarding/upnp.

So In my home setup I have a server with plex media server installed on it. This application needs a open port to allow remote access to my files on it. I had this setup and the application acknowledged I had access. However when remotely accessing my files the bandwidth was capped (I think this due to a plex specific reason).

So after trying out a whole bunch of options (e.g. d downgrading etc) I finally disabled software flow offloading and voila it did the trick.

So I am wondering if there is a reason why it is causing this? Is it the way how plex sets up the remote connection and this doesnt work with flow offloading? Is there another setting I missed to fix this?