Inconsistent results from Smart groups using relationships (results change after a time period)

To recreate on Demo:

1)
Search >> Advanced Search
In "Contact ID" field enter 174
In "Display Results As" select "Related Contacts"
Choose relationship type "Household Member of"
Save results as Smart group
Call the group "Cruz Household" (3 results)
2)
Search >> Advanced Search
In "Contact ID" field enter 174
In "Display Results As" select "Related Contacts"
Choose relationship type "Household Head of"
Save results as Smart group
Call the group "Cruz Household - Heads" (1 result)
3)
Search >> Search Builder
Make a group that includes both previous groups
a) "Contacts" "Groups" "=" "Cruz Household"
b) also includes contacts where "Contacts" "Groups" "=" "Cruz Household - Heads"
This combined group should have 4 results.
Call this group "Cruz Household - All"

Wait a little bit of time (possibly for the smart group rebuild job?)

Go to Contacts >> Manage groups
All of the above Smart groups show 3 contacts instead of 3,1,4 contacts as expected.

Clicking on the contacts link beside the group name in Manage Groups returns the wrong contacts. For example the group "Cruz Household - Heads" shows the contacts from "Cruz Household". Clicking on "Edit Smart Group Criteria for "Cruz Household - Heads"" returns the correct results (1 contact).

Possibly related: Error in logs is "Notice: Undefined index: operator in CRM_Core_BAO_Navigation::getMenuName() (line 468 of /home/mysite/public_html/sites/all/modules/civicrm/CRM/Core/BAO/Navigation.php)"