Hello there, @Jonfs.
There aren't any similar reported cases about this issue with the bank register display window.
To better isolate this, I recommend trying a couple of basic troubleshooting steps to get you back on track. Let's start using an incognito window to determine if it's the browser that's causing the error.
Google Chrome: press Ctrl + Shift + N
Mozilla Firefox: press Ctrl + Shift + P
Internet Explorer: press Ctrl + Shift + P
Safari: press Command + Shift + N
If it works, let's clear your browser's cache. This is to delete temporary internet files and data that's causing unexpected behavior in the product. Otherwise, you can try using a different browser to refresh your QuickBooks.
Let me share a link on how to clear the browser’s cache: https://community.intuit.com/articles/1145697.
Stay in touch with me if you have any other questions when working with QuickBooks. I'm here anytime you need help.
