I'm having the same problem on my V+ box. Only seems to happen on hd channels, and mainly sports rather than, eg, 108. It seems to be random, but when it starts, it happens intermittently at regular intervals. Switching to the non hd channel causes the fault to disappear. But I prefer to watch on hd, particularly sports. I should be grateful for any help or advice that can be offered. Thanks.
As with all the above posters, if you have a technical fault, ring it in.
You'll get an immediate response if you give them a ring on 150 [VM phone] / 0345 454 1111 [non-VM phone] (from 08:00 until midnight, every day), or use the Contact Us link at the bottom of this page to initiate a live chat (from 08:00 until 20:00, Monday to Saturday)
This is primarily a user community forum and while the VM Forum Team do endeavour to read and, where appropriate, respond to every thread, it can take them from a few days to a couple of weeks to wade through the volume of posts. So for an technical issue, which this seems to be, your best line of inquiry is through the Faults team via the methods above.
I've tried all that you suggested. I've always struggle on the phone because of my disability, that's why I prefer to do it online but nevertheless I tried to phone them, and after struggling to get my message across they didn't even offer to send an engineer out, and I've been trying to use the live chat for the past week but I just can't get through, it's a total waste of time. These people don't care, all they're interested in is your money, once they've got that they refuse to deal with you, refuse to do any repairs yet they'll happily rake your money, so I intend cancelling my subscription, if they want to talk to me then I'll be happy to talk to them but I can't see that happening.