Thanks for posting on the community. I'm sorry you're having an issue with your television blacking out.
I have had this trouble myself in the past with various devices and it's usually down to what's known as an 'HDMI handshake' issue. It's where the data is not processed properly when the two devices are connected. It can cause black screens to intermittently appear, weird greeny, magenta strokes across the picture and all sorts! Not a good time.
This seems to be the case because you have identified that changing the HDMI socket resolves the problem.
I do believe that this is an issue that is more widespread than people realise, but luckily, I do believe Samsung support can be of assistance. You can find the information here but the main bit from this thread is this little golden nugget from Samsung "one of our representatives can remotely access your TV to perform the HDMI EDID rewriting before establishing the connection with the V6 box and the other HDMI-supported external devices".
Hopefully this resolves the issue for you. One thing we did used to suggest, is changing the video output settings on the V6 / TiVo box to 1080p passthrough, as this helps, especially when switching between resolutions on different channels.
I hope this has been helpful, please do let us know how you get on or if you manage to find an alternate fix to the problem!