Inconsistent data following user exit!

What causes this issue?

The system executed a user exit to valuate a CO-PA line item.

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

The following data was saved:
Point of valuation &v1&
Number of user exit &v2&
Line items: operating concern &v3&
reference document number &v4&
You cannot change any characteristic values during valuation, since that
could lead to inconsistencies (e.g. profitability segment number and
corresponding characteristic values are different -> incorrect
report data).
In Customizing for Profitability Analysis, check the valuation strategy
assigned to the point of valuation &V1&. The program contained in the
user exit &v2& may not change characteristics (that is, it can only
change value fields).

System Response

The valuation could not be carried out.

How to fix this error?

Make sure that the user exit &V2& only accesses value fields.
If you want to change characteristic values, do this using the user exit
for derivation. A separate component for this is stored for this in
SAP project management.

Error message extract from SAP system. Copyright SAP SE.