Error when linking two predecessor tasks to one successor task
Symptoms
When linking two predecessor tasks to one successor task, the following error message appears:
The number of days between the predecessor task and the successor task does not match the specified lag time.
Reason
When a task has two predecessor tasks that end on different dates, the start date of the successor task is ambiguous. Using the end date of one of the predecessor tasks could violate the link definition for the other predecessor task, and vice versa.
Resolution
Open the dialog box to define the properties of the links. Enable the "Successor can start any time" option for both predecessor tasks.
When you set this option, the start date of the successor task can be calculated based on the latest end date of a predecessor task without violating the rules if the other predecessor task ends earlier.