QCI check results are inconsistent

What causes this issue?

Once a default set has been created, it has to be activated before it is
used for quantity conversion calculations. During activation, the
Quantity Conversion Interface (QCI) checks the set for consistency. A
trial quantity conversion is carried out. If a set is not consistent, in
other words would lead to an error message within the QCI, it cannot be
activated. The parameters have to be changed so that the trial
conversion does not fail. Once a set has been activated, it can no
longer be deleted.
In this case, the QCI has carried out the quantity conversion, but the
resulting quantity differs from the transaction quantity, although the
units of measure are identical.

System Response

The default set cannot be activated.

How to fix this error?

Check the QCI conversion using the desktop calculator function
(Transaction O3QCITEST).

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.