Hello Arduinos!
Okay, thanks to your help and few changes in the programming I have stable code here.
Everytime I pass the light barrier, one of the normal videos (1,3,5,7,(9)) moves to the disturbed pair video.
BUT:
a.) I think a made a mistake in using the random function. It choosing only the pairs {2,3},{4,5},{6,7}. The Arduino, after having it work half an hour, never chooses pair {8,9}. I thought always that the random function is 0 indexed, isn't it?
b.) Did I make the right definition here? Before I had it like [][2], but then is miss the vertical values, don't I?
code
int remotePins[4][2] = {{2,3},
{4,5},
{6,7},
{8,9}};
code/
Thank you again for your time and you words. I appreciate it. Meanwhile I will again try to really understand 2D-arrays! 