This isn't the kind of experience we want for you. Let me help sort this out so you can use QuickBooks and get back to business.
Let's start with your concern about the customer's address keeps disappearing. The information that shows in the customer's transactions, such as the address is based on the information that is setup in the customer's profile. If you only add the address in the check, that change reflects in your current transaction only.
Let me show you how to enter the complete address of your customer:
Select Customers from the top menu bar.
Choose Customer Center.
Double-click the name of the customer.
Enter the complete address in the INVOICE/BILL TO and SHIP TO fields under the ADDRESS DETAILS section.
Meanwhile, aside from manually changing it in the vendor's profile, you can also update it when you go to the 1099 Wizard. Choices made in the Select your 1099 vendors page, can remove or add the checkmark in the Vendor eligible for 1099 box.
However, if the address is already in the customer's profile or you did not go through the 1099 Wizard, we'll do a few troubleshooting steps to get past this unexpected behavior.