This still happens to me:
If i add a launcher to the panel by right click - add to panel and then right click on the new launcher and choosing “move” there is at least a 1 / 3 chance the panel freezes so I have to kill it.
If I just create the launcher and then go into Panel Settings and reorder the items on the panel that way it always works.
Anyone else have this problem? It never happened in 4.14 for me.