Enrollment Overrides allows enrollment in an invalid plan

My client has discovered that employees are being enrolled in an invalid plan option sometimes.  It's happening in Enrollment Overrides though the doc says "When you make an option invalid, that option does not appear on any enrollment form, whether print or online, and no employee can enroll in that option."  These invalid options are shown in the visual assist as a valid selection and Enrollment Overrides allows the enrollment.   There's nothing to indicate to the user that the option is invalid.   I'm being told this functions as designed.    It's causing problems for my client because employees are being enrolled in invalid plan options and unless someone happens to notice and fix it, the employee's medical benefits aren't being calculated properly.  I'm being told