You're welcome
The reason it does that is because when the first wall collision happens, the enemy starts moving the other way, not touching the wall anymore, but then the next tick the enemy mirrors itself, and is now touching the wall again, making it move the OTHER way, and un-mirroring itself, and the process repeats. Hope the pictures help.
[attachment=0:2nut63bc][/attachment:2nut63bc]
P.S. The blue dot is the enemy's origin point, the red arrow indicates the direction of the enemy's movement, and the green box is the wall collision happening.