I made a program using the wrist camera, gripper, and digital output that worked before. Recently, it started showing the following compile error: "name 'nb_occurence_0' is not defined". Pressing advanced view allows me to look at the script which contains the line throwing the error. To make the program work, I have to comment and uncomment blocks of my program at a time, until eventually, it all starts working. What is the issue behind this error?