WebCenter dropping random supplier invoices (rejected but not showing in rejection table)

Summary

WebCenter dropping random supplier invoices (rejected but not showing in rejection table)

Content

We have found that a handful of invoices for suppliers are dropping although others for that same supplier process accordingly (even on the same day).

Items to note: All suppliers have one address, multiple sites with the same address in order to process invoices through different Business Units

We have verified all users have the same default BU in their setup.

When running the Import Invoice Job we are leaving the BU blank to process ALL business units.

Still cannot figure out why certain invoices are dropped?