BizDoc table primary key TNPK_BIZDOC_DOCID violation

We have experienced a rare problem with the BizDoc table in TN. In some cases we get a primary key violation error when we try to persist a new document in TN. It seems that webMethods Integration Server is re-using values for the DOCID column in the BizDoc table. This results in an error:

java.sql.SQLException: [MERANT][SequeLink JDBC Driver][Oracle]ORA-00001: unique constraint (TN.PK_BIZDOC_DOCID) violated

Do you know of a patch to this problem or a reason why this is occurring? Thanks in advance.

I usually get that kind of error but we always found out that it is because of different Document Type or Processig Rule. (not quite sure it this helps you)