sensorstick 9 dof and mpu6050 multiplexing

Hey all,
I am currently having some trouble with an Arduino project. These are the sensors/hardware that I am using:

mpu6050 breakout board (https://www.sparkfun.com/products/11028)
sensorstick 9dof breakout board (https://www.sparkfun.com/products/10724)
Flexiforce pressure sensor-just in analog pin
16 channel multiplexer (SparkFun Analog/Digital MUX Breakout - CD74HC4067 - BOB-09056 - SparkFun Electronics)

Arduino Due

What I want to do is read raw data from these sensors simultaneously (or close to). I have been able to read data off of each sensor individually and I have been able to read data off of them all at once but not consistently. I know this is probably something to do with my multiplexer or arduino code. The weird thing is that one time when I plug it in and read data off of the serial terminal it all works, and then the next time I restart my computer it doesn't. When it doesn't work it is only one of the mpu6050's that do not work it reads all 0's. The sensorstick will also read all 0's for only its accelerometer values. I would really really appreciate any help on the subject. My code is attached.
Thank you in advance for any help!

mpu6050_sensorstick_flexiforce.ino (8.19 KB)