Comparing the stack trace in https://bugs.launchpad.net/ubuntu/+source/metacity/+bug/792999/comments/5 to the one in https://bugs.launchpad.net/ubuntu/+source/metacity/+bug/797078/comments/2 shows that this is the same as bug 797078.
Perhaps private bug 793981 (which "Apport retracing service" had automatically marked this bug as a duplicate of) is really the same as bug 797078 as well.
Comparing the stack trace in https:/ /bugs.launchpad .net/ubuntu/ +source/ metacity/ +bug/792999/ comments/ 5 to the one in https:/ /bugs.launchpad .net/ubuntu/ +source/ metacity/ +bug/797078/ comments/ 2 shows that this is the same as bug 797078.
Perhaps private bug 793981 (which "Apport retracing service" had automatically marked this bug as a duplicate of) is really the same as bug 797078 as well.