This happens when you are watching a programme live that you are also recording. My understanding is it is the buffers being cleared at the start and end of the programme.
Since I record virtually everything I watch I see this quite often but, since I use the standard recording defaults, i.e. 1 minute before and four afterwards, I rarely see it on the programme I am watching.
Nice to be able to post again, after their mistake (removed by the Censorship team). ¡No Pasarán!
Yes, it is still freezing for a second when the recording starts/stops. It also pops up the banner showing the programme name etc.
This is not a new thing as it has done it since it was installed. I would have expected it to do the recording in the background with no indication on screen that anything is happening (that is what my old V+ box did).