Since Fedora-Rawhide-20160913.n.1 , yelp fails to run at all in an installed system:

[test@localhost ~]$ yelp
WaylandCompositor requires eglCreateImage and eglDestroyImage.
Nested Wayland compositor could not initialize EGL

(yelp:2816): Gdk-WARNING **: Error 71 (Protocol error) dispatching to Wayland display.
[test@localhost ~]$ 

The first two messages are not new - they show up in 20160912.n.0, where yelp runs OK. The third message - "Error 71 (Protocol error) dispatching to Wayland display." - is new, it does not appear in 20160912.n.0.

abrt doesn't catch a crash, but it definitely doesn't really run. This prevents the 'Getting Started' welcome tour from appearing on first login.

Quite a lot of bits changed in the 20160913.n.1 compose, including gtk+. Here's the obvious ones:

Package:      glib2-2.49.7-1.fc26
Old package:  glib2-2.49.6-1.fc26

Package:      gnome-shell-3.21.92-1.fc26
Old package:  gnome-shell-3.21.91-2.fc26

Package:      gobject-introspection-1.49.2-1.fc26
Old package:  gobject-introspection-1.49.1-2.fc26

Package:      gtk3-3.21.6-1.fc26
Old package:  gtk3-3.21.5-1.fc26

Package:      mutter-3.21.92-1.fc26
Old package:  mutter-3.21.91-2.fc26

Package:      webkitgtk4-2.13.91-1.fc26
Old package:  webkitgtk4-2.13.90-1.fc26

A full list of changed packages is in https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/UFCHYA4XYMTCIDJQUTJJFJGKBWZI4WNU/ .