NI 9401 undesired digital input level

Hi NI community,

I am using NI 9401 on cRIO-9074. According to the datasheet of NI 9401, the Low level and High level are 0.8V max and 2V min, respectively. It means it should work well in conditions of noise tolerate about 500mV (peak-peak of noise is 500mV max). After incorrectly reading pulses from a motor driver, I tried to set up a NI 9263 (analog output) to check the input levels of NI 9401. It resulted that the state was ON at 1.4V and OFF at 1.3V. Could you please explain why I got the result and how can I mitigate it.