I have been this very similar issue with my vu+ duo2 also that i think you had. I have noticed that the SNR is jumping around.
I have noticed that if I run a speed test on a device connnected via wifi (my iphone) then it glitches a lot during the download but becomes completely frozen during an upload.
As soon as the speedtest is finished the picture comes back. This is the the same for FTA channels also.
Something on the line is causing glitching when the internet is being used for downlaoding/uploading/streaming.
The annoying thing is that when I connect the VM box I can't see the issues, even if I start downloading/uploading so complaining to VM is not getting me far lol.
What I know for sure is that if I remove the LNB that connects the router to the splitter so it's only TV there are no glitches and all is well so it's definitely something VM have done. Possibly an update or other change in thier infrastructure for my cabinet/area.
Any ideas what this could be or any solutions to this yet?