semanage commands fail with SELinux: Could not downgrade policy file

Issue

When running semanage commands to modify default selinux policy, the following error message is displayed:

  # semanage fcontext -a -t unconfined_exec_t /usr/sbin/httpd
SELinux:  Could not downgrade policy file /etc/selinux/targeted/policy/policy.24, searching for an older version.
SELinux:  Could not open policy file <= /etc/selinux/targeted/policy/policy.24:  No such file or directory
libsemanage.semanage_reload_policy: load_policy returned error code 2.
SELinux:  Could not downgrade policy file /etc/selinux/targeted/policy/policy.24, searching for an older version.
SELinux:  Could not open policy file <= /etc/selinux/targeted/policy/policy.24:  No such file or directory
libsemanage.semanage_reload_policy: load_policy returned error code 2.
/usr/sbin/semanage: Could not commit semanage transaction

although the policy file exists:

  # ls -lh /etc/selinux/targeted/policy/policy.24
-rw-r--r-- 1 root root 7.7M Sep 23 12:34 /etc/selinux/targeted/policy/policy.24