&4 Order (& &) already exists. Mode field set to 'U' (Update)

What causes this issue?

If a securities order that already exists in the database is delivered
in insert mode, the system overrides the mode field at check intensity
= 2. The system therefore changes the mode field MODE from 'I' (Insert)
to 'U' (Update).

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.