I recently had an AD7799 fail after connecting a load cell to Ain1 while the chip was powered up. The connection was a 4-wire connection to Ain+, Ain-, Vcc, and Agnd. The connection was made by plugging in an insulated wire to board connector, so the actual pins were never touched. This damage happened while the ADC was powered on. I have never had trouble when it was powered off. When it happened, I was not aware of any static discharge either. I also have 1k resistors in series with the analog inputs.
Is this a fluke occurrence? Are there any caveats I should be aware of when hot-plugging a load cell? What additional protections should I implement?