Cause
This error occurs if a control on a form does not have the required associated reference property defined. Every control that is painted on a form requires a property reference, using the name of the control, to be added to the form class.
This problem usually occurs because the .ddb (forms definition) file associated with a schema has not been loaded.
Action
Load the .ddb file, and then identify the problem forms by performing a schema validation on the forms.
If a mismatch still exists for a form, replace the form with a prior valid version of the form from a database backup.