Update participant flag on Project Change Order using Groovy

Hi, we're writing a trigger in Application Composer, Project Change Order object. It is supposed to add a participant and assign actions based on new value of Reason attribute. The trigger is starting as expected, creates new row in Participants region, adds a ResourceId and after clicking save the results are visible in UI and a new record is returned by a select query from PJE_CHANGE_PARTICIPANTS_B table. However, when we try to update any of the flags the same way (AssessmentFlag, ImplementationFlag, ApproveFlag or ReviewFlag) to 'Y', the checkbox is not selected after clicking save in UI and values in