Default Enrollment formula not working as expected

We are in process of Benefits for US. One of requirment is, for the loss of eligibility life event we want to default the enrollemnt option from "Family" to "Employee + One" when there is only one eligible dependent. We have created Default Fast Formula and associated at Program Plan Type level.

The Evaluate Life Event process inserting "Employee Option" to the enrollment instead of "Employee + One"

We could see from Evaluate life event participant process log that Fast Formula returns "Employee + One" .
However, it defaults to "Employee Only" by "Enroll in Default Benefits" process which runs after the Evaluate Life Event participant process.