Outbound Campaign API 400 when filtering by legal hold metadata

Looking for advice on isolating outbound dialing records that intersect with our legal discovery holds. The goal is to ensure that no agent is dialing into numbers currently flagged under hold, but the Analytics API returns a 400 Bad Request when the filter object includes legal_hold=true. The error message states Invalid filter criteria for campaign_id, yet the same filter works for standard voice recordings. Is there a limitation on combining campaign filters with custom metadata in the current Genesys Cloud 2024-Q2 environment?

Thanks for the help.