When you need to store a BLOB or CLOB type object into your database table via view objects (based on entity object) you need to make sure following two things should be there:
1. EO Batch mode must be turned off. Make sure there is no BatchUpdate tag is present in the EO.xml as sometimes jdeveloper fails to remove it and things looks fine on Entity object overview page.
2. Make sure there is no programmatic or declaratively in view object tuning section vo.setForwardOnly(true) set. BLOB and CLOB type object saving needs some special processing and need to go back to the same row in VO more than once. So setting this will fail to store these objects.