TL391B: What's the hysteresis?

Hi Team,

I am using TL391B in a simple application. 1Hz square wave are input to non-inverting port, while a fix voltage are applied to inverting port, and TL391B are powered by 3.3V, see schematic in below:

We get test waveform in below, CH1(Yellow) are non-inverting port, CH2(Blue) are inverting port, and CH3(Red) are output. We can see the Vout is ramdom here. 

I go through TL391B and only find the offset are 4mV level, so I don't know what's the root cause of it, maybe the hysteresis is quite large of TL391B? Could you help to guide me on this case? thanks a lot!