Subsequent to the 1.6 update, the controls for Windows 10 Edition were changed. Preceedingly, (when using a mouse) one functioned as  "side attack/place" and the other "break/use item". While this may not, in fact, be a bug, many players (much like me) were used to the syntax mentioned beforehand. It would be suggested that either players have the option to choose the controls more profoundly, or the controls are switched back to how they used to be. Thank you.