Beam 'Hitboxes?'
Currently, as I have seen as of Musescore 3.6.2, the 'hitbox' (best way I can describe it without knowing the actual term, the area that when clicked, highlights the beam) is a rectangle, so I can click far from a beam, as long as its within the rectangle that lines up the corners of the visual beam. This can be annoying when I'm clicking between two staves of a piano score where the beam of 4 coupled 16th notes is pointing down, and I attempt to click and drag to view a different part of the score and instead end up accidentally highlighting the beam and then stretching it out when not having clicked on the beam.
Comments
Edit > Preferences > Canvas > Proximity for...
Indeed, the selection areas are generally rectangular. it's not clear what you are trying to click instead, but to select an element that is obscured by another element - even if not truly obscured, just overlapping selection areas - use Ctrl+click to successively select each item in a stack. Sounds like you might be trying to simply drag the canvas? This works, but really isn't a good way to navigate, not just because the risk of selection something accidentally like this, but also because it is incredibly limited and inefficient. Much better to simply use the mouse / scroll wheel or the many other ways of navigating your score (eg, Home/End/PgUp/PgDn, or the Timeline or Navigator, etc).