It seems that under some hard to reproduce conditions, when trying to change the keyboard shortcut for a command, the settings dialog crashes. There is a Fedora bug for that which contains data collected by ABRT (like backtrace etc.) which may be useful: https://bugzilla.redhat.com/show_bug.cgi?id=1368348
See this Xubuntu 17.04 https://bugs.launchpad.net/xfce4-settings/+bug/1656530 note that not only does it crash but it removes the setting completely
Marking this report as duplicate of the newer Bug 15958. *** This bug has been marked as a duplicate of bug 15958 ***