I actually figured out what causes this with the Atomo. Since the button button is recessed and floats, your finger can become the ground sometimes on the Atomo, hence why Gilles stayed with a spring for a little while. It's nothing that would be a concern, but for some it can cause discomfort.
Your what becomes a ..............Huh?

If you are the ground the mod has worse issues than a Spring could fix.
No matter the switch position, bottom/side/recessed - Making Contact with Battery WHILE keeping contact with the main body of the mod is what makes a switch work.
Best switch in the world would be useless if it had no connection.