Unbalanced AR Invoices created from Billing

 We have a new BU setup for AR. We are loading invoices into AR from Billing and Billing is set to directly create GL entries. In the Groups created at AR side, AR distribution code is blank and on creation of accounting entries in ITEM_DST, only AR row is created. As a result unbalanced entry is created with only debits. But still the accounting entries are complete and posted to GL. I find this very weird and the resulting journals are failing at GL side. Any idea why this is happening.

When we create invoiced from Billing, are they supposed to have blank distrib code? If not, why this is happening. please advice