The solid style buttons on the page appear to have a border which often disappears when the button is clicked making it suddenly look thinner, and isn't clickable which means you can sometimes click what looks like the button and nothing happens.
I can fiddle around with CSS to fix this, but I wondered if I have missed some simple Wappler setting for the button which prevents this from happening as it isn't a great user experience!
I checked the sandstone theme: Bootswatch: Sandstone and it doesn't do what you show in your gif, so it's something in your CSS causing this.
Maybe you can provide a test page link so i can tell what's wrong.
I found the problem… it was a line of CSS which doesn’t show up in the Wappler Styles menu as it is in a CSS file referenced by the main design file specified in the project settings.
So if you have such a CSS structure, best to use Chrome Dev Tools to find the answer to this kind of question!