When adding any launcher to top panel, the panel freezes. Only the mouse will work.
I tried with all compositors. They all react the same.
Then pulling up a terminal and resetting the panel works, but the launchers are gone. If I ‘replace’ the panel, that works but the terminal is then tied to the panel.
Update: If I just add launcher to the desktop then the panel again freezes. Also resetting the panel sometimes causes a crash. I added a bug report #1604490 for that one.
UPDATE2: If I just move the launcher using my mouse to either the panel or Desktop, than the panel does not freeze. Only right-click move to panel or desktop does it freeze.