# 500 error when creating MR and API request (Severity 2) **Problem**: Customers received 500 errors when creating merge requests or making API requests to their projects, especially those with the Credits add-on enabled. The root cause has been reverted and the fix is now deployed to production. **Impact**: Projects in namespaces with the GitLab Credits add-on could not create merge requests or access their projects through several API endpoints, including /api/v4/projects. Over 15,000 errors occurred, blocking affected customers from these features. Customers with many projects (e.g., around 100) faced significant manual work to apply the workaround. As of now, the fix is deployed to production and customers should no longer experience 500 errors, but direct customer confirmation is pending. **Causes**: A recent code change to the Duo Code Review feature introduced a bug, where an incorrect call to the Feature.enabled? method caused a NoMethodError during API serialization. This affected projects in namespaces with the active GitLab Credits add-on, resulting in 500 errors when accessing multiple API endpoints. **Response strategy**: We advised affected customers to temporarily disable the GitLab Duo feature at the project level as a workaround. A revert merge request fixing the root cause was created, reviewed, merged, and is now fully deployed to production. Monitoring confirms error rates have returned to normal and previously failing pages are accessible. We are awaiting direct confirmation from the initially affected customer before marking the incident as resolved. _This ticket was created to track_ [_INC-8530_](https://app.incident.io/gitlab/incidents/8530)_, by_ [_incident.io_](https://app.incident.io) 🔥