I admire you for sharing the details of your concern with us, @dataforge.

I'll make sure you'll be able to print your open invoices flawlessly. I recommend logging out and logging back in to your QuickBooks Online (QBO) account to refresh the system. Then print your invoices again.

I've attached a screenshot below for your visual reference. 

If this is not the case, I suggest logging in to your QBO via a private or incognito window. This way, we can rule out a possible browser's cache issue. 

There are times the browser is full of cache and cookies and can affect the performance of your account. Using a private window helps us verify the issue as this doesn't store any data files.

To open an incognito window, you can refer to these keyboard shortcuts keys:

• Ctrl + Shift + P for Mozilla Firefox & Microsoft Edge browsers
• Ctrl + Shift + N for Google Chrome browser
• Command + Shift + N for Safari browser

If you're able to print your invoices, I recommend clearing your regular browser's cache to refresh the system. If this is not the case, I suggest using other supported browsers to narrow down this matter. 

let me also add this link that you can read for reference in case you want to learn how to modify your invoices: Customize invoices, estimates, and sales receipts in QuickBooks Online.

You can count on me whenever you need help with your invoices or QuickBooks. Please don't hesitate to leave a comment in your reply and I'll get back to you as soon as possible. Have a good one!