Material (&1) assignment can be changed, but it will cause inconsistency

What causes this issue?

The changed material assignment is used in a recipe, which will lead to
data inconsistency.

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?

If you don't need to change the material assignment really, just create
a new one and use the newly created assignment in the recipes in the
future.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.