My V6 is always put to standby when not in use. When it's switched back on it switches off and on several times over the first 10 minutes of use and then settles down. This happens any time the V6 box has been in standby.
It's not an HDMI issue as it's the same cable that has been used since the box was first installed around two years ago.
I've switched off and done a full reboot a couple of times, but it makes no difference.