Error while dereferencing a variable interest rate

What causes this issue?

Within gap analysis, the system encountered an error in the variable
interest rate reference for a bank transaction.
The identity of the financial transaction is contained in the next
error message.
The system was unable to carry out the necessary calculations.

System Response

The cash flow for this bank product was not analyzed.
The analysis results therefore do not contain all the data.

How to fix this error?

Check the variable interest rate specified.

System Response

Error message extract from SAP system. Copyright SAP SE.