WIthout being able to see all your code I can't try out my solution but the problem appears to be that you are recreating a new vid[][] array for every sequence name.

In Java a 2D array is an array of 1D arrays (and they don't have to be the same length.

Try the following code

1. PImage[][] vid = new PImage[vidName.length][]; // create array of arrays
   
2. 
   
3. for (int i=0;i<vidName.length;i++) {
4.   vid[i] = new PImage[picNum[i]]; // create inner array
   
5.   for (int j=0;j<picNum[i];j++) {
6.     String name = vidName[i]+"_"+j+".png";
7.     vid[i][j] = loadImage(name);
8.   }
9. }

Ah, thank you so much for your swift answer! Spent an embarrassing amount of hours on that bug... Cheers!