Restrict Enrollment into multiple benefits programs

We have a requirement that an employee is eligible for three different health programs (X,Y,Z) and he can chose to enroll in one of the programs. If the employee does not enroll before the enrollment period, he would be enrolled by default into Program Y.

The Max Plan enrollment is set to 1 at the Plan Type level to restrict enrollment into multiple programs, the system is throwing an error that max plan enrollment is not met at the plan level if the employee tries to enroll in a different program. However, the employee/ben admin will have to uncheck the default enrollment and will have to complete the enrollment to satisfy the Max Plan enrollment condition.