What you were expecting to happen, and what actually happened:
Click on a button or an unitand it works. If the mouse moves a the tiniest bit, it doesnt register as a click any more. (MouseUp event on the same object that got MouseDown, should always trigger the button).
Clicking and trying to be fast is quite annoying. Sometimes it takes multiple attempts to click anything. No issue when matching gems though.
How often does this happen? When did it begin happening?
Steps to make it happen again
Click on any button, but move the mouse at the same time a tiny bit.
Naturally this depends in part on your mouse sensitivity, but there does always need to be some sort of tilt threshold movement before the program registers it as a click-and-drag instead of a simple click.
This can also occur with touchscreen inputs, as a tap-and-drag is a distinct gesture from a simple tap.
But there’s another complication: It depends on where the game implements “click” vs. “mousedown/up” events internally. If the game listens to mousedown/up events directly, then yes it is the game’s responsibility to determine which gestures do (and do not) constitute a proper “click”. On the other hand, if the game listens to “click” events only, it is the system (the OS and/or Unity engine) that determines whether a given gesture is or is not a click.
Mouse and DPI settings are fine. The problem lies in game behavior, that during clicking the mouse cursor has to be almost completely still (i think it allows 1-2 pixels of movement for clicking).
Going left and right during Gnome-a-palooza or something, trying to be really fast, the mouse might move a little bit more during clicking. The clicks wont register and have to move the mouse back again. Please add more slack to click movement or consider the MouseUp event to always click the object.
A simpler/more elegant fix is to mirror what other games do: Instantly run a widget’s associated action on MouseDown, completely ignoring the MouseUp event (except for dragging gems on the board, of course). Also makes the game feel more responsive.