Variable key for condition record not found (internal error)

What causes this issue?

The system was unable to read the variable key (containing data on the
condition record, such as the key combination, e.g. supplier/material)
for a condition record. This is probably due to a program error.
The number of the condition record concerned is &V1&.

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?

Contact your system administrator.

Error message extract from SAP system. Copyright SAP SE.