Worked on the symfony/symfony repository to address a bug affecting dynamic collection forms during the PRE_SET_DATA phase. Focused on ensuring stability and correctness of form data, the developer updated the ResizeFormListener to manage a stack of collection children added at this stage, preserving their state and improving data integrity. The solution was implemented in PHP, leveraging event-driven programming and robust form handling techniques. Comprehensive unit tests were added to validate the new behavior and prevent regressions. This work reinforced the reliability of the Symfony Form component lifecycle, particularly in complex scenarios involving dynamic form collections and data synchronization.