On Time Delivery Rate

I’m a new seller on Amazon. I’m selling FBM. I received notification that the “on time delivery” metric is now being used to account for account health. This is a metric we struggle with. Our understanding of it is Amazon determines the on time delivery by the dates they set based on the default shipping. We ship from multiple warehouses and each have different inventory levels. When we go to confirm shipment we can change our shop from to any of our warehouses, but it doesn’t update the on time delivery date making many same day shipped packages, arrive outside of Amazon’s delivery rate. This negatively impact ODTR putting our store as risk of becoming FBA only as per Amazons policy next week.

Has anyone else run into this? How did you resolve to improve your ODTR to be within amazons guidelines.