When you're in the FITS viewer and use a mouse scroll wheel to zoom-in, if you're not careful and scroll it too much, which is easy to do with Apple's POS scroll mouse it will ultimately lead to a crash. It zooms too far and appears to causes a memory leak as I've seen memory usage spike.
I've accidentally flicked the mouse on that screen, it would zoom way in or out then Kstars became unresponsive at first followed by a crash some time later. The solution is to not use that mouse and it works fine with another one. The mouse seems overly sensitive and possibly the software needs to ensure it doesn't accept input past a certain point.