If the Project Status Items reports a weak overall RMS mark residual this means the RMS of the largest (worst) Marking Residual from all the points in the project has exceeded the threshold listed on Project Review Settings Dialog.
A large RMS residual is an indication the project is not solving within the thresholds selected. This is usually caused by poorly solved camera positions so verify the project’s photos are solving well by checking the Photo Status Items on the Project Review Pane.