Error when processing a characteristic value assignmt with change number

What causes this issue?

The processing of characteristics using change numbers requires a number
of processing steps.
An error occured during one of these steps. The system cannot process
the characteristic correctly.

System Response

The system switches to display mode.

How to fix this error?

Exit the transaction and repeat the steps that led up to the error using
a different property. If the error continues to occur, the problem is
probably located in the classification system.
Repeat the step without entering a change number. If you can assign a
value without a problem, you probably have a problem in Product Safety
and Stewardship. If the error continues to occur, you have a problem in
the classification system.
Notify your system administrator.

Error message extract from SAP system. Copyright SAP SE.