Undershoot on I2C bus
We have some fairly extreme undershoot on the I2C bus when operated (close to) 1MHz (i.e. "Fast Mode Plus"), out of spec.
Propose adding a couple of series resistors (max. 100ohm is recommended in "I2C bus specification 1995") to damp the undershoot in the next hardware rev. Until then, we'll drive the bus at 400MHz maximum.