Comment # 9 on bug 1030828 from Atri Bhattacharya

Fred and/or Ulrich, do you have any extensions installed? I know of at least
one that causes the occasional crash and reload of gnome-shell leaving a
coredump behind, namely the "Random Wallpaper" extension. But there may be
others. Does starting with all extensions disabled (e.g. from gnome-tweak-tool
-> Extensions) help?