After working for a certain period of time, the automatic processing job configured on the SMP stopped working. When manually processing the cubes on the SQL Analysis server, it was noticed that some dimensions for the Tasks cube were not processing.
Dimension [Task] cannot be saved
The data set used to generate the Task dimension had grown to be larger than 4GB.
The workaround for this is to remove the Task cube from Processing.
To resolve the issue, the SQL server version must be a Enterprise Version, or a Data Center version, and the dimension must have its StringStorecompatibilityLevel property set to 1100. See https://docs.microsoft.com/en-us/sql/analysis-services/multidimensional-models/configure-string-storage-for-dimensions-and-partitions?view=sql-server-2014 for instructions on how to do this.
This cannot be changed on a SQL Server Standard version.