Character conversion from code page & to & for IDoc failed

What causes this issue?

Code page $1 was used to archive the Intermediate Document data. When
it was reloaded, it needed to be converted to system code page $2. This
conversion failed. (ABAP translate)

System Response

The Intermediate Document data cannot be processed.

How to fix this error?

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

Error message extract from SAP system. Copyright SAP SE.