Create a "A" variable to generate random numbers every second, every tick, whatever you prefer.
Create a "B" variable to generate random values.
Create a Instance variable "C" on your enemies that will hold any value.
For each enemy you spawn, set it's stance variable "C" to the value of the variable B.
Then every tick, or every second, or whatever you prefer, compare the values of "C" for each enemy in game. And then set a command to whenever "C" has the same value of "A" simulate the enemy's jump.