Document Extraction service creates a zero byte DOC-SPLIT-1 under certain circumstances. One such is when the persistence of the business process (BP) is low, for example BP Start Stop - Engine , a zero byte file is extracted.
Resolving the problem
As a workaround change the document storage to File System for that particular BP.
This issue has been fixed in patch 5020401 (18.104.22.168) of Sterling Integrator