3.3V I2C Logic on 1.8V Device
It's possible there is an error in the datasheet and the SCL/SDA and INT pins should not be pulled above VDDIO because of protection diodes. That would exactly explain the symptoms you are seeing. The datasheet refers to pullups to VDDIO (which, as you know, is limited to about 2V) in several places. 

I suggest you contact the manufacturer and confirm. To get this to work, assuming I'm right, you'll have to add voltage translators such as the PCA9306 between the MCU and the chip, as shown in the schematic Figure 7. The INT line will also need voltage translation.