Element overlap issue when using default enrolment rule that changes the previously enrolment option

Summary:

A HSA plan has 'Single coverage' and 'Employee + Dependent coverage' options, each with a separate Standard Rate because the contribution limits differ. The Employee Standard Rate use calculation method Flat Amount with Participants enter value during enrollment and the Employer Standard Rate use calculation method Flat Amount. Both the rates feed the same payroll element/input value. The issue is with the Employee standard rate.

When a life event defaults a currently enrolled participant from 'Employee + Dependent' option to 'Single coverage' option using Current - Default, New - Default or a Default Enrollment Fast Formula, processing fails with Element Overlap. The same option transition works when default enrolment rule is