TCA6424A: Different results when reading same configuration register multiple times

Hi we are wondering if there are any certain registers/steps we need to do before we can use the TCA6424A for output? When we read from Output Port 0 it returns different values each time we read it. 

We use 0x23<<1 as device address,

0x0c as register address (Configuration Port 0 with auto-increment disabled),

and we first write 0x0 and 0x0 as the data values for both high and low to Port 0. 

But after we do this and try reading the output register (0x04) multiple times, each time a different value is read. Does anyone know why this is happening? Thank you