You may encounter a situation where health check stays in a down state even though it is not failing. Here is an example of what you may see in the sysinfo:
Due to a bug, existing IP level health checks aren't deleted during an upgrade, but rather are marked as "disabled and report sick".
The fix is available from 126.96.36.199. However, the issue still remains after upgrading from 6.5.7.(188.8.131.52) to 184.108.40.206 and higher, because the registry content still keeps the old container which should have been removed during a DNS update on an health check.