Qduino Mini battery monitor has stopped and no I2C data

My Qduino project was working well until I accidentally connected USB power with the LiPo disconnected. I can now only get the program to run by disabling the fuel gauge setup and WirebeginTransmission in my code. Have I fried my Qduino or is there a way back from this, please?

I have dismantled the project and rewired the external I2C device. The fuel gauge is also an I2C device, so does that point to either Wire or a hardware failure? I haven’t got a scope to play with - is there an easy way to check whether SCL or SDA is being dragged low?

The problem with the fuel gauge went away when I disconnected my external I2C device, so this must have been holding one of the lines low. I’ll replace this external part and see what happens…