Horrible smear effect on Mac

I've been using MuseScore 2 Beta 1, and have just moved to Beta 2. So far, loving it. However...

In certain circumstances, you get a horrible smear effect. This can most readily be seen by opening a few pallette options and then scrolling the pallete up and down by dragging the scrollbar, or by (on OSX) three finger swiping right to show the applications screen and then three finger swiping back left. I'm running a virtually brand new MacBook Pro with 16GB memory, so it isn't a system limitation - the screen just isn't redrawing properly.

Thanks, and otherwise keep up the good work (and I look forward to some bulk lyric-moving functions!)

Stuart