Foreign key constraint on same table not allowing to delete on DB2

Question

I have table named VARIANT_LINK_BUILD_CHANGE where primary key column name is VARIANT_LINK_BUILD_CHANGE_OID and foreign key is also in same table named SWAP_VL_BUILD_CHANGE_OID.

The data looks like this:

VARIANT_LINK_BUILD_CHANGE_OID    MOD_TYPE     SWAP_VL_BUILD_CHANGE_OID
    22269                         ADD           (null)
    27510                         DELETE        (null)
    32399                         DELETE        (null)
    32400                         MODIFY        (null)

Here , when I try to delete the above records using the query

DELETE FROM VARIANT_LINK_BUILD_CHANGE 
WHERE VARIANT_LINK_BUILD_CHANGE_OID IN  (22269, 27510, 32399, 32400);

I get this error:

[Code: -532, SQL State: 23504] THE RELATIONSHIP FK_VARIANT_LINK_BUILD_CHANGE_SWAP RESTRICTS THE DELETION OF ROW WITH RID X'000001270C'. SQLCODE=-532, SQLSTATE=23504, DRIVER=4.28.11

I am not sure why getting the above error since foreign key values are null. Can anyone help with this?