Just curious, do you turn the camera with the left mouse button?

At the end of my previous mouse's lifespan I had little control over the left-click function. When I hold it down, sometimes it'll click multiple times (no sound, just metal contacts wearing out). So what happens is I have the tank selected, but when I turn the camera with the left mouse button it clicks. The tank gets un-selected and my untargeted heals heals me instead.