SAP Note 26690 - No conf. quantity after changing unit of measure

Symptom:

After changing the unit of measure of an order item, the confirmed quantity is missing.
Or:
After changing the conversion factors of an item, the confirmed quantity is calculated from the old required quantity and not the required quantity from the confirmed quantity.

Cause and prerequisites

The availability check is not active.

Solution
As a workaround, it is possible to avoid the error by temporarily changing the order quantity and resetting it again.