A team member increased the estimated completion time for their activities on the critical path.

Conduct a root cause analysis (RCA) and plan the correct actions to ensure completion of the tasks on time.

Allocate another resource to help the team member to complete the tasks and meet the estimated activity time.

Train the team member in the methodology to get the sufficient knowledge to meet the estimated activity time.

Apply crashing to the strategic tasks to recover any time that was lost to bring the project on track.