Yes. If you built a UPNP spammer, it could effectively create a persistent DOS. Considering how many corporate networks rely on UPNP for printers and the like, you could really make life hell for IT departments if you were to embed this in a malicious invoice.
Yes, I thought it's behaviour was something like a DOS attack. If you did it deliberately it certainly would be.
I am no Windows fan, but this behaviour by the TV seems to be unreasonable.
If you’re designing a device that’s going to sit on a network, you need to build it to handle unreasonable peers.