Field & & will not be transferred from the account assignment template

What causes this issue?

You have created an account assignment template in which the field
status for the "&v1&" "&v2&" field has changed from "Required Entry" or
"Optional Entry" to "Hide".

System Response

The field value from the account assignment template is deleted when the
field status is currently set to "Hide". The document can then be
posted.
If the field value of a hidden field is derived from other data, the
document can be posted with the value derived.
If the field value from the account assignment template is changed
manually or if a new value is entered in a field with a field status
currently set to "Hide", it is not possible to post the document.
INCLUDE 'CUSTOMIZED_MESSAGE_INFO' OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.