Crosstalk through I2C
What is your I2C speed? Depending on the speed and distance, I2C can go as low as 1k for high-speed low-impedance bus. See http://www.ti.com/lit/an/slva689/slva689.pdf

What do you exactly mean by:


  The crossing only occurs at the sensor's end of the cable (less than 1 inch), not in the middle of it


By "crossing" the wires, the good practice consists in not having the two I2C lines running side by side. For example, this is bad practice for a long ribbon cable:


  
  VCC
  GND
  SDA
  SDL
  


A "better" way of doing things:


  
  VCC
  SDA
  GND
  SDL
  


This way, GND shields SDA from SDL. However, GND itself can generate noise if the bypassing isn't sufficient on either side of the cable.

The best way would be to have additional wires, for the sole purpose of shielding the signals:


  
  VCC
  GND
  SDA
  GND
  SDL
  GND
  


This is used on all IDE ribbon cables for example.