unable to simultaneously use i2c and PowerUp

I'm communicating to the nPM1300 eval kit over I2C from an nRf52833 DK (running a fuel gauge application). This works well until I connect PowerUp (through USB) and enable the fuel gauge, then I2C comm breaks down and I get red messages on PowerUp, like:

09:16:11.953   npmx charger termination_current get => Error: IO error. Error: unable to get termination current.
09:16:13.450   npmx buck gpio retention index get 1 => Error: IO error. Error: unable to get GPIO config.
09:16:17.340   Reset cause: SWRESET
Similarly, if I disconnect the i2c wires, PowerUp works fine.
Are these incompatible in some way?
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