Hi CSV
See SAP note 456458 point 10. on this issue.
In VBOF only a document type can be used in field TVFK-BLART, for which
an internal number assignment is defined. If an external number range is assigned
you run into F5152. VBOF is creating a NEW FI document so it has to create a NEW
So when you run VBOF you can maintain for example FI-Doc.type AB to avoid the error.
Hope it helps
Kind regards
Brian