How to predict when Jack-in-the-Box zombies are about to explode in endless survival?

Question

These zombies are pretty easy to kill, only it seems that sometimes they explode prematurely and take down a whole bunch of plants.

So what are the signs that they are about to explode and what triggers explosion?

Answer 1

I believe their explosion is entirely random at each step. However, you know that they are about to explode because they stop a moment before and have a startled look on their face.

Answer 2

If you hit a lot of damage to them, they will explode much later. And they stop before it explodes

Answer 3

I dont play the endless version that much, but the explosive zombies are un-predictable. You can only tell because they stay still and get a weird expression on their face.