Hi there,
I have exactly the same problem. I did not know about the problems in combination with the Serial, but I did find an odd thing happening. When I run the program with Serial Monitor it works fine, but at a certain point the output of the board to the TV is only black. Also the Serial printing stops. When I close and open the Serial Monitor the Arduino seems to reset itself and it works fine again.
Fiddling with the R4 doesn’t change a thing unfortunately.
Kind regards,
Thomas