Need to setup rate start date to after 12 month for new hires in Disability plan

We have a requirement wherein the rate and coverage for disability plans should start after 12 months for new hires. We have create the formula for this calculation and associated it to new hire event and the start dates are calculating correct.

However, post the New hire event if there is any other event prior to the 12 months then the rates and coverage start dates are overridden to as of event. This is not aligning with the New hire rate and coverage start dates as the employees is getting enrolled into the disability plans prior to the actual start dates for rates and coverages.