When you use OEPE to deploy to the OSB, you might run into this problem during deployment:
.FileNotFoundException: /oraclesoa/Middleware/user_projects/domains/MY_DOMAIN/osb/config/sessions/ALSB_IDE_Internal_PublishOp_1313998-1275/_binary/SessionData/singleton (No such file or directory)
This problem occurs when your session is invalid or been corrupted. You can fix this by going to MY_ORACLE_HOME/user_projects/domains/MY_DOMAIN/osb/config/sessions/ and remove or rename the directory involved. After this, restart your managed server and the problem should have been fixed.