You cannot change item &1; item is already allocated (see long text &2)

What causes this issue?

The article is allocation relevant. There exists an allocation for this
document item and item cannot be changed due to one of the following
reasons:
Field check customizing is not maintained.
Based on the field check customizing, changing the item is not
permitted.
Contract release orders exist for this contract item.
Outbound delivery exists for this item.
Changing an article is not permitted.
Item category is not enabled for deallocation.
At least one of the VAS items is allocated; changing this item is not
permitted.
Allocated confirmation exists for this PO item, changing the item is not
permitted.
Changing the Returns Item flag is not permitted.
Assign same rule for supplying and receiving plant in the customizing
for stock transport order.

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?

Maintain deallocation settings at item category level in Customizing for
<ZK>Maintain Item Categories for Fashion Management</> under
<ZK>Logistics ? General -> Sales and Distribution -> Sales -> Sales
Document -> Sales .Document Item</>.
Maintain deallocation rules and assignments for current
cross-applications documents (Sales Order, Stock Transport Order,
Purchase Order, Goods Receipt, and Goods Issue) in Customizing under
<ZK>Logistics ? General ->SAP Fashion Management -> Order Allocation Run
(ARun) -> Cross-Applications</>.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.