Reminds me of the time we were trying to bring up a new PCB with a handful of I2C devices and it just would not work. I'd done the driver for one device, and my colleague for another.
Too far longer than it should have to work out that they were using the same address. Fortunately one of them had a pin that would add 1 to the address, so that saved the day.
https://i2cdevices.org/addresses http://www.coris.org.uk/jdc/Notes/i2c-devices.html