Cannot update baseline for in progress activities

Hello PPlanners,

I do have a problem with successive baselines: while updating a project, I create a new baseline every month after updating the project

Now some activities are late; say, they will start 2 weeks after the Original Start Date, or finish 4 weeks after the Original Finish Date: Baseline 2, which I have created and assigned after the update, displays correctly for the activities not yet started, B2 Start Date and B2 Finish Date are correct; but the same Baseline 2 still displays Baseline 1 Start and Finish dates for the In Progress Activities

Can somebody explain why?

Thanks, Alexandre