There is a bug with Fake Out when using alongside U-Turn
It happens specifically if you throw out a Pokemon with it, use it, and then use a move like U-turn to get out
and then the Pokemon you swap into from the u-turn gets one shot by the enemy,
then you swap back into your fake out user
and try to use fake out again, which should work cause you've swapped.
Although it ends up failing and doesn't end up working.

Have tested this on 6.3.4 and cannot reproduce it at all