How do I stop my enemies walking off a platform

I have added edge marker sprites to the platform like it says in the beginners guide and the enemies will hit the edge marker and go in the other direction but after a few times it will just walk through the sprite. I am new to construct 3 so any help would be gratefully appreciated.

Usually this is caused by the collision polygon or origin image point location on the enemy sprite. When it collides with the marker and turns, it immediately collides the second time and turns again. To avoid this issue, make sure the collision polygon is rectangular and origin point is in the middle.

Also, you can add a cooldown - for example, after turning, don't allow to turn again for 1 second. Use Timer behavior for this.

I changed the collision polygon for the enemies and that worked a treat, thank you very much for your help.