Yikes! In attempting to rewrite Si4703 control code, to remove the wiringPi dependency, I seem to have come up with a way to crash the controls on the board. It appears to only affect the I2C controls as I can continue to listen to the radio station. I believe that it's in the breakout board because the problem survives reboot of the Raspberry Pi and reseting the I2C bus has no affect. It will only go away if I interrupt power to the breakout board.