beaming eighth notes across lines makes beam disappear and causes inappropriate line spacing that cannot always be undone with Ctrl+Z

Steps to reproduce:
1. write eighth notes that go on for more than a line (enough so that a line break happens automatically)
2. select them all and select beam middle

At this point the beam will disappear. Doing things like pressing X to flip the stem direction or changing the title of the score sometimes will increase the space between the lines every time you do it and create other unpredictable behavior. In some cases this can cause one of the lines to go off the page and not show up on another one. The spacing changes caused by this cannot always be undone.

I've inserted a version of my score before the bug and then after. In the before version you can select the eighth notes in measures 32-37 and press beam middle and then this bug will happen. Trying to undo will not correctly undo the beam change (everything in measures 32-37 goes back to how it was but a beam disappears from measure 31) and the spacing between the lines will increase.

Also, another bug caused by this is that if you go on the "after" version of my score, select one of the eighth notes on the last line, press X to flip the stem, and then save the score with Ctrl+S (for some reason if you save the other way this won't happen), it causes a significant graphical glitch that looks like this:

This one will go away once you press anything.