I appreciate the details that you've given, @Candi2.
This is not the kind of experience that we want you to have. Let me provide some troubleshooting steps to get rid of the black & white lines that are showing on your register and checks.
Normally, verifying and rebuilding your data can help fix issues like this. Since this isn't your case, I'd recommend uninstalling the software and running a clean installation. This allows QuickBooks to create a new folder to replace broken installation files.
Before doing so, please create a back up of your company file to avoid accidental data loss.
Here's how to do a clean install:
Here's an article you can check out to know more about installing QuickBooks using clean install: Reinstall QuickBooks for Mac Using Clean Install.
Once done, try checking your checks and see if it works this time. If not, I'd suggest contacting our QuickBooks for Mac Technical Support Team. They have the tools to review the logs of your company file securely and can help you resolve this hitch.
Please keep me updated how things turns out. I want to ensure everything is up and running for you.