Ive only have seen it when i was trying to push a enemy that was likely going to guard. (Noted i did them also as the first target)
I was using the weapon to make them fear, but the enemy was not in fear state, so it should had not been able to evade.
When i pushed them, they showed that they used up guard state instead of getting stunned. Has happend a few times for me now, but not often.
Ive also tried when they were affected by fear, and even though they used guard in that state, they didnt always get counterd.