Port Groups - Problem with port.ignore association ruleset

We have a port group with association ruleset "port.ignore equals 0" that is returning 0 ports in the group. Previously this group contained ~600 ports.

Tried inverting the association to "port.ignore equals 1", and also had 0 ports.

/opt/observium/db.log has several messages: 

[2018/07/20 12:50:05 -0400] discovery.php(32553): Failed dbQuery (#1052 - Column 'ignore' in where clause is ambiguous), Query: SELECT `port_id`, `devices`.`device_id` as `device_id` FROM `ports` LEFT JOIN `devices` ON (`ports`.`device_id` = `devices`.`device_id`) WHERE( ``.`ignore` = '0') AND `ports`.`deleted` != '1'

We tried running the query shown in the log in the observium DB directly. If we modify the query like this, it seems to work: "SELECT `port_id`, `devices`.`device_id` as `device_id` FROM `ports` LEFT JOIN `devices` ON (`ports`.`device_id` = `devices`.`device_id`) WHERE( `ports`.`ignore` = '0') AND `ports`.`deleted` != '1'"

Unsure if related, but when we try to rebuild the group, it doesn't appear to work. We end up at http://observium.nepacil.local/groups_regenerate/action=update/ with message "Building Group Memberships"