Number of business objects not found: &1

What causes this issue?

Database inconsistency: There is at least one business object which is
not found. The details can be found in the full log of the conversion
report (RNGC_CONV_REF_CHAR), where the IDs of the non-existent business
objects are indicated with warning messages.

System Response

The reference characteristic values of these business objects can not be
copied to table AUSP, therefore they are skipped.

How to fix this error?

The database inconsistency can be eliminated by two ways:
+,,Create the business object (which does not exist currently) with the
exact same object ID and object type (if the classification UI is
triggered during creating, the conversion does not need to be run
again).
Or:
+,,Erase the database entries referring to this non-existent business
object from tables INOB and/or KSSK and/or AUSP. In this case the
conversion does not need to be run again.
Be aware, that if the used class type is a multobj=true class type, then
KSSK.OBJEK and AUSP.OBJEK are the internal object IDs matching in table
INOB.CUOBJ (the true object ID is INOB.OBJEK in this case). If it is a
multobj=false class type, then KSSK.OBJEK and AUSP.OBJEK are the true
object IDs.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.