The import file or data source contains more rows than allowed by the system property 'com.glide.import.max_import_set_size' which defaults to 10,000 rows. (high likelihood)
Multiple concurrent imports to the same import set table are accumulating rows beyond the maximum limit. (medium likelihood)
The import set table already contains data from previous imports and the new data would exceed the total row limit. (medium likelihood)
A custom import script or integration is attempting to insert more records than the system allows in a single import set. (medium likelihood)
The system property has been manually reduced below the current import set size after data was already loaded. (low likelihood)