Customer invoices are blocked for dunning automatically when we run F150

HI All

when we are running the dunning (T.Code F150) for one of the customer invoice items are blocking for dunning automatically.

the customer master setting for dunning block fields is empty and there is no changes for this field.

These invoices are created recently and could please help to find a solution for not happened the same in hte next dunning runs?

thanks in advance

Best regards

Venu