Bug in ArduinoISP example code when writing large blocks of eeprom data: When writing to eeprom, the circular serial buffer gets overwritten when writing more than twice the length of the serial input ...
Use the 6-pin ICSP header on Arduino Nano (best reliability): ICSP Header Location on Nano: ┌─────────────────────────────┐ │ ┌──┬──┐ │ │ │ │ │ ← = Pin 1 ...