I’m sorry you’re having problems with the GNSSDO display.
It sounds like: either the OLED Qwiic cable has come loose; or the OLED itself has failed. Either way, the ESP32 is not able to detect it on the Qwiic bus (hence the “Illegal display i2cBus” messages).
Please:
Disconnect any cables you have attached to the front of the unit
Remove the four screws securing the front panel
Gently remove the panel
You will see the OLED display taped to the rear of the panel
A standard Qwiic cable connects it to the main PCB
Check that the cable connectors are seated correctly at both ends
Replace the panel and screws and retry the firmware
If that doesn’t fix it, let me know and we’ll get a replacement OLED sent to you. That will be quicker and easier than you returning the unit for repair, if you’re OK with that?