The most common error says something along the lines of "client does not match the data on the server", this means someone else has affected the project schedule after you opened it but before you tried to save it.
Best practice would be to first take the project out of production by changing the Project Status to one that is not active (i.e. Estimating). Then refresh the project and make your changes from there.
Keep in mind that while you can Lock a project schedule, there are security rights that can bypass this option. Also, Traffic Screens can update any project in the system, and individuals can have an effect on the project schedule when entering time in the My Task widget or Calendar.
- Please refer to our General Errors guide for more information.