PCM1864 EVM only seeing 17 bits of data

I have a PCM1864 EVM. I put it into mode 1 with no other changes. It is set up for I2S mode and 24 bits of data by default. I see an LR Clock of 96kHz and a bit clock of 6.144MHz. But I only see the 17 MSBs of 24 bits toggling on the PCM1864 DOUT pin. I have done a number of other experiments including using slave mode, setting a 48kHz sample rate but all cases the 7 LSBs of the 24 bits never toggle, they are always 0. I see the same thing when set up for 20 bits of data. When I set it up for 16 bits of data I see all 16 bits toggling. If I capture the I2S data it looks good. When I feed audio into CH1L and CH1R and play back the captured data it sounds good. But I have not found a way to get the 7 LSBs to do anything. They are always 0. Please help.