Unexpected Plan Regression in SQL Server 2022 CU10 After Query Store Forced Plan Enabled

Question

Hello

After upgrading to SQL Server 2022 CU10, we noticed a sudden performance regression on a stored procedure that previously ran fine. We had Query Store enabled with a forced plan applied for stability & it was respected correctly until this update.

Post-patch, the same query now appears to ignore the forced plan intermittently, especially under high-concurrency scenarios. We confirmed that the last_force_failure_reason_desc shows "Unknown", which isn’t very helpful. Checked https://learn.microsoft.com/en-us/sql/relational-databases/performance/optimized-plan-forcing-query-store?view=sql-server-ver16 for reference .

We tried clearing and re-forcing the plan; which temporarily restores the expected performance, but the problem eventually reappears. Extended Events show plan recompile triggers are normal (stats update, etc.), and MAXDOP settings haven’t changed.

We suspect this may be related to query optimizer enhancements / Query Store behavior changes introduced in CU10. However, there’s no mention of such behavior in the release notes, and we haven’t altered the database compatibility level. I’ve also reviewed relevant materials from Microsoft SQL Server Trainingbut haven’t found anything addressing this specific behavior post-CU update.

Has anyone else experienced this? Are there any undocumented behavioral changes with plan forcing in the latest cumulative updates? Would appreciate advice on best practices for ensuring forced plans remain stable across CU upgrades.

Thank you!!