Bad layout of beam with first note set to beam middle
Open the attached 2.x score in version 3. There is a floating beam in measure 1 that appears to be connected to the group of four eighth notes in that measure.
(At this point, you can delete the group of four eighth notes and the floating beam will also disappear.)
Perform a relayout by moving a note up and then down in pitch with the arrow keys. The floating beam will move to measure 12 and one of the beams that should appear in that measure is missing. The space between the lines will also become very large.
If at any point, you click on either the beam of the four eighth notes or the floating beam and move an end handle, the program will crash.
Also, if you delete the group of four eighth notes (after performing a relayout), the beam will initially still appear.
(Tested in version 3.0.1)