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.