So inserting new records works fine as far as the feature geometry, but no attribute values for that new feature can be set when performing the initial insert. However, you have no issues setting attribute values for records that already exist. Do I have this right? When you insert new features, you could perform a Store() directly upon inserting the new geometry followed by an update of the same record using set_Value and another Store() operation. In other words, if you know updates work fine but inserts are challenging because attribute values aren't respected (only geometry), then treat the newly-inserted record as an update rather than trying to set the attributes on insert.