I am trying to highlight some text in the a pdf generated with latex, however sometimes it misbehaves and selects an entire region. Below is a gif which shows the effect I'm having (I tried to scroll to "remove" the blue selection which was left over). Is this a problem with the generation of the pdf? or perhaps macs "preview" app?

Edit: I have tried this in the "skim" app on mac and have the same problem.