AD7176-2 Data read errors

I have the AD7176-2 Eval board and I'm getting frequent errors when reading data. About 1 out of every 200-500 data points is wrong. I have the input set at 0 V which is mid-scale, so the output is normally around 8,500,000. The bad points are way off- like 281, or 261,007. I see that the AD7176 has an option for CRC checksums to verify read/write data. Is reading bad data a problem with this part? What is causing it?

BTW, I am sampling at 10 Hz, although the problem occurs whether I sample faster or slower.