When changing the quantity of configurable material in the transaction, following error is shown and the quantity is reset to old value.
CRM_CONFIG 304 ‘The change to field QUANTITY was declined by the configuration”
The user is not allowed to change the quantity of the configurable material anymore if the quantity has been changed by the configuration. Generally, all the fields that are ever changed/influenced through configuration can only be changed via configuration. The other fields still allow manual change as long as no configuration is changed.
This is a standard behavior. The check is introduced in CRM_CONFIG_CHECK_FIELDS_EC since rel 6.0. In order to change the quantity outside of the onfiguration you need to do a modification in CRM_CONFIG_CHECK_FIELDS_EC. You can comment the part for * schedlin and with that you allow your user to change the quantity. This is considered a modification to the standard functionality.