What’s going on with UI lately? The X and Y coordinates have to be exactly the same on mouse button down and mouse button up. It’s impossible to click on buttons using my Wacom tablet. I remember having struggles on Samsung’s website once, with emoji selection on KDE, and with some UI elements in Bitwig. It’s kind of annoying—I have to click multiple times and keep my hands extremely steady.
In my opinion, as long as the mouse cursor stays within the area of the button, the button should trigger the on-click event.