We do see rare reports of assertion failures in the krb5int_key functions,
which handle an internal table of thread-specific data keys.

Ticket 8614 (which you linked to from the stackoverflow answer) happens because
krb5int_key_register() is called on a key that is marked as already registered.
A candidate explanation there is two different versions of libgssapi_krb5 in
the same process, both calling into the same libkrb5support, although I'm not
sure that's right--although it's easy enough to have multiple versions of
libgssapi_krb5 installed on a machine, they should all have the same soname
(since we haven't changed it in a long time), which I think would make it
difficult to load more than one version into a process.

The failure reported here is the inverse: krb5int_key_delete() is called on a
key that isn't marked as registered. krb5int_key_delete() is invoked from the
library finalizer of libgssapi_krb5 (also the finalizer of the krb5 version of
libcom_err, but typically the e2fsprogs version of com_err is used on Linux).
Although it's possible for the finalizer to run without the initializer having
run, there is a check for that. So I don't have any good theories.