I too have an intermittent problem with the display,
with random red dots flickering on the screen. My initial assumption is that it is the video card on the Pi. The supplier disagrees, but I am running out of tests to do....
The red and blue dots appear at different places on the display, usually not on startup, but after the board has warmed up.
From the suppliers response my testing confirms:
It is not a Media format decode issue - This happens for all output from photos, to videos and the main menu.
It is not a power issue - the same problem occurs with both the supplied and a 2A USB battery supply
It is not a cable issue as the same thing happens with different HDMI cable
It is not the Tv (Samsung Series 6) as can be duplicated on a monitor or projector...
Last thing to try is the HDMI signal tweak.