Adding new Additional Field Throws Off Alignment

I’m adding in a select field in the “Additional” tab and it’s causing the State and Zip fields of the Billing tab to appear below my new field added in the Additional tab. Now when I remove the new field, the State & Zip fields still remain in the Additional part of the screen instead of the Billing section.

please help

https://wordpress.org/plugins/woocommerce-checkout-manager/