We have reported this bug on several occasions dating back to 2019 but it still exists as of Oct 03, 2023

After adding a customer in the POS module, and creating a sale, then pressing the tender button, the payment details screen pops up. (The customer gets created in the database at this time)

By pressing the cancel button to review the sale for whatever reason, then pressing tender again, the payment details screen pops up. (The customer gets created in the database AGAIN). 

Cancel, tender, cancel, tender, cancel, tender........... Duplicate customer records keep getting created. 

It appears that the order of operations for creating the customer in this module is poorly designed and could be easily fixed to rectify this problem.