I just installed eOS and tried to rearrange the screens. Once I rearrange the displays in the menu, so that my main display is to the right and not to the left, the mouse buttons stop working.
I have two matching LG displays and also tried the LXRandR app, but the effect was the same. Once you rearrange the displays, you can only move the mouse cusor but the buttons don't work. The keyboard still works and I was able to return to the previous settings this way.
Mouse: Logitech M215, Keyboard Logitech K330
It doesn't happen if you log out/ restart so I guess it's a problem with the desktop enviroment.
I hope you can suggest a solution.