Each module has a number of I2C devices that it controls. When a module is communicating with such a I2C device, then the module is a Master on the I2C bus. At that moment the I2C bus is occupied.
Is there a "main" and a "internal" I2C bus ? How can I see the difference in the source code ?
What is the file "isl28022DL.h" ?
I'm sorry, but I think that you have no idea how much trouble you are in.