If I understand correctly, you were using a fully optimized table and later decided to add the pzPVStream BLOB column to the table. If that is indeed the case, the Pega platform always considers the pzPVStream column as the source of truth. Since that column is currently empty (or NULL) for existing records in that table, you would end up with errors.

To fix the problem, you will need to write an activity, which can use Obj-Browse or Report Definition to read all the records in the table from only the optimized columns. Then iterate over each of these records and call Obj-Save on it. Obj-Save should update the BLOB column as well. Note that for this work effectively, please this table needs to have pzInsKey and pxObjClass columns.