Originally Posted by sub
...could you be running any firewall/antivirus/net-nanny type software that could be causing issues? These all manipulate network data sent to/from applications.
I did have some old access rules in the router to try to block add banners. I disabled those (I don't think they worked anymore anyway) and so far so good :-) Hopefully, that was the problem! Thanks!
Well, I guess I was too optimistic. Same thing happened again. The only other thing I can think of is the port forwarding for port 8866. But if I disable this then I can't access NPVR externally. Windows defender is the only anti virus running.