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Might just be temporary network issue but it appears Vodafone are aggressively throttling traffic over ports 563/443 (commonly used for SSL Usenet). Easy to get around by routing the traffic over a VPN but kind of annoying to have to mess about. It is not a surprise given the unlimited data SIMS - probably Vfe are seeing lots of usage by a small number of people. Of course Vfe might start throttling VPN traffic at some point so whack a mole really.
Most of my traffic goes over VPN anyway but was not sending SSL usenet traffic over VPN as it is already encrypted and just a waste of router CPU cycles - looks like that is no longer the case.
Early indications are that running the Usenet traffic over the VPN is working much better - I was getting lots of dropped packets before and contention. Hiding all traffic in a VPN appears to beneficial as it limits the extent of ISP shenanigans.