TCA6408A: Only 4 outputs at once?

I am evaluating the TCA6408A.

The program resets the TCA6408A, configures the outputs and then writes from 0x00 to 0xFF.

Outputs are pulled-down through 10k resistors. A logic analyser records the I2C signals and the outputs levels.

• It only works when 4 outputs are selected: first four, last four or mixed four.

• When selecting more than four, no output responds.

I haven't find any notice about outputs limitation on the data-sheet.

How to use all the 8 ports as outputs?

Thank you!