The guard's timer read the sensor while G28 ran; bdpressure.py writes the
probe mode at every homing move, and Klipper allows only one I2C request
at a time per device: KeyError ('i2c_response', 1), Klipper shut down
during HOME. The guard now wraps the sensor's i2c in a reactor mutex at
connect; bdpressure and bdpressure_check (now looks up sensor.i2c at
every use) go through it too.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>