Problem with adding a record to the Relationship tab from a Java PX in 9.3.5

From an Event Java PX, I have code to add a record to the Relationship tab of an item using the following code:

ITable reltable = agilePart.getTable(ItemConstants.TABLE_RELATIONSHIPS);

IRow rowRel = reltable.createRow(mfrPart);

It works fine in my 9.3.2 system but after upgrading to 9.3.5, I am getting the following error:

Error code : 20271

Error message : Invalid Update Relationship Event Filter. No target object class ID was specified.

Root Cause exception : com.agile.admin.client.value.AdminException: Invalid Update Relationship Event Filter. No target object class ID was specified.

Does anyone know what this error means and how to fix it?