UPnP recursively fetches all content on discovery.
When VLC connects to UPnP device, in my case llink's upnp implementation, it fetches ALL media. Essentially a recursive list.
With ~10,000 files and folders, the initial scan takes about 15 minutes, creating an unreasonable load on the UPNP server.
The majority of UPNP clients and players treat UPNP as a virtual filesystem, and only show the root container containers, and items.
The current implementation in VLC is unrealistic and unreasonable. Please consider a more network friendly approach.