Sound out of sync in stream box

Hi I have recently had virgin installed and the sound is out of sync with the picture, some channels are worse than others. Its is also out of sync when using apps such as Netflix and YouTube. I have altered the audio delay to its maximum on my tv but this is still not enough. When watching tv via apps on my tv and not through the virgin stream box I have no issues so it is not a problem with my sound set up. Anyone got any ideas.  I have seen lots of discussions from people with the same issue and it sounds like it is a problem virgin haven’t solved yet.