Strange Monster Movement

I was attempting to create a random choice for my little purple monsters to move left or right for a few seconds, then idle for a few, then choose left or right again. Can anyone help me understand how to correct my mistakes? The monsters will make the initial choice successfully, but then they get all wonky and either flicker between states, or simple fail to leave the idle.

Here's a video of the results

https://youtu.be/GXqC6oyoze4

Would something like this work for you?:

https://www.dropbox.com/s/t9btkztlopfsj ... .capx?dl=0

I think it refers to the movement of vibration

https://www.dropbox.com/s/sqhly33mpam90 ... .capx?dl=0

Thank you both! I'm gonna try these out and see what I can do.