In nearly a decade testing with Quicken H&B, I can't recall anyone ever reporting your problem before. I have never seen it in my H&B versions going back to Q2010.
I'm curious; why do you have to key in the Customer/Vendor name for your payments; why can't you just select the desired name from the Customer/Vendor dropdown?
I suggest you create a New (test) Quicken file. In that New (test) file, add a checking account and an Accounts Receivable (Customer Invoice) account.
In the New Quicken file, initiate the New invoice / Receive Payment process that has not been working for you in the past.
Does the "Payment - Customer Invoices" dialog come up with the Customer name already displayed in the Customer field (and the appropriate invoices listed below)? Is the checking account displayed in the "Deposit to" field?
If the process works as it should in the New Quicken file, that suggests to me some problem with your regular Quicken data - a problem which Validate can't correct. [You can try a super-Validate on your regular Quicken file, though I have little confidence it will help. After opening File > File operations; hold down CTRL+SHIFT while clicking "Validate and Repair". Put a checkmark in "Super validate file" and click OK.]
Also please provide more details about your Quicken data file.
I'd like to know if you have account registers where a single account is approaching or exceeding 16,000 transactions.
And I'd also like to see the "File Information" window (See below)
Is any cloud backup software actively accessing your Quicken data file while Quicken is running? What is the complete file name of your Quicken data file (e.g. C:\Users\username\Documents\Quicken\QDATA.QDF)?
How much total RAM do you have installed?
What version of Windows are you running?
About file size and number of transactions:
You can find out how many transactions you have in your data file by doing this: - Click Tools / Account List. This should tell you how many transactions you have in each of your accounts in an optional column, "# of Transactions". If this column is not shown in the Account List, click the Options button at the bottom of the Account List window, then click "Number of Transactions" to add the column.
- Click Help in the Menu Bar. CTRL+click About Quicken and it'll give you a File Information box. Please capture an image snapshot of this File Information box and attach it here. The Windows Snipping Tool (available with Windows 7 and newer) can be used to capture a partial screen image and save it to a file of file type PNG, JPG, or GIF.
To attach the image here, start composing your response. At the top of the text entry window you'll see a row of icons beginning with B I S Click the landscape "Attach image" icon. It will allow you to select and upload the captured image file from your computer. The captured image will be inserted at wherever the cursor is located in the text.