Value of modific. counter for doc. &1 in SCM is: &2, but should be: &3

What causes this issue?

During a synchronous ATP check that was called from an external system
for an item of document &V1&, the system discovered that the document in
the external system might contain changes that have not yet been
replicated in the SCM system. This has been determined by comparing the
values of the modification counters in both systems:
External system: '&V3&'
SCM system: '&V2&'
This situation can arise, for example, if the replication of document
data in the SCM system is slow.

System Response

The system does not allow you to execute a synchronous ATP check that is
called from the external system for any items of this document. Due to
technical reasons, the ATP check therefore returns 0 confirmations for
these items.

How to fix this error?

Once the document data has been successfully replicated in the SCM
system, the modification counters will match.
If, for example, the data has not yet been replicated because it is
still waiting in the queue in the qRFC layer, you must wait for the
completion of these queues before you can execute an ATP check.

Procedure for System Administrators

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.