The SET[] array is defined as uint8_t SET[8] = {0, 0, 0, 0, 0, 0, 0, 0}; which means that SET[8] is clearly out of bounds. In order for this to work, SET[] would need to be 9, not 8. https://github.com/IdleHandsProject/addr_7seg/blob/cfaeb689d977158ce2af1f46e602f8c91ca01c00/Firmware/addr_7seg_demo/addr_7seg_demo.ino#L125
The SET[] array is defined as
uint8_t SET[8] = {0, 0, 0, 0, 0, 0, 0, 0};which means that SET[8] is clearly out of bounds. In order for this to work,SET[]would need to be 9, not 8. https://github.com/IdleHandsProject/addr_7seg/blob/cfaeb689d977158ce2af1f46e602f8c91ca01c00/Firmware/addr_7seg_demo/addr_7seg_demo.ino#L125