Question: Do I need internal_eeprom.hex I never flashed that on the mcu and it still does work. what is internal_eeprom.hex, is it only for a factory reset?

It contains patches 1…16, and more importantly initial settings for MIDI channel, filter type, etc.

since we can set it on first use we don’t need it then. the first 16 patches are in the factory_data.syx