Definition of General Valuation Classes for Current Portion incorrect

What causes this issue?

Multiple general valuation classes are marked as
<DS:DE.TPM_FLG_CURRENT_PORTION_HTM> Current Portion of Long Term
Debt/Asset (CPLTD).</> This is only possible if a source valuation
class is assigned to all the valuation classes marked as current
portion. In the source valuation class itself, the current portion
handling cannot be activated.

System Response

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

How to fix this error?

Ensure that you only activate the current portion handling for one
general valuation class in
<DS:SIMG.BEWERTUNGSKLASSEN>Define and Assign Valuation Classes</> or
assign a (non-CPLTD) source valuation class to the marked valuation
classes.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.