I have the same problem. Looked all over the internet for a solution and everyone asks the same questions to your problem without giving a cure. Basically there is no difference in my set-up apart from i switched isp to Vodafone. Then boom speed dropped to 2.6Mb on wired mag, router syncs at 56.8Mb, all devices over wifi in close proximity show tests at 45-55Mb.
This obviously causes stuttering on viewing.
This points to 3 possible causes, the mag, the router or the isp. The router is showing all ports closed and impossible to open any, not sure if this could somehow be a problem or some other setting in there. Quite a bit out there on net that infomir have incorporated something into their software via copyright infringement laws. Next, maybe the isp can slow iptv traffic, if so i have no clue about how this works and how to get around it. But as most complaints on the internet are from Vodafone broadband customers, it is definitely them in someway.
Amazing how it started about 4 weeks after i had been with them, so it was too kate to walk away, now i am trapped with a shoddy iptv service or paying out for more equipment.