Error in value of property "defaultButtonId" of element "&1"

What causes this issue?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

The value of the property is incorrect.
This means that either
a) An element that does not exist has been entered.
b) The entered element is not a button.
c) The entered button is not a child element of the checked container.

How to fix this error?

Change the property so that a button that is a child element of the
checked container is entered.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.