Hi,
Welcome to our forum and thanks for contacting us with your question!
This is how cluster points work, they stack when zooming in and will get the points far enough apart when zoomed in. If they are exactly at the same point, they will be permanently stacked. Therefore, what you can do is move the points slightly so that they are not exactly in the same position.
Demo: https://jsfiddle.net/BlackLabel/yfLu2q0e/
I hope you will find it useful
Best regards!