How do I fix 'WFBackgroundShortcutRunner-ErrorDomain' preventing scanning or copying between Mac and Brother printer?

Try this

Clear System and Network Blocks

• Reset Printing System: Go to System Settings > Printers & Scanners, right-click or Control-click the device list, and choose Reset printing system. Re-add your Brother device.
• Check Local Network Permission: Go to System Settings > Privacy & Security > Local Network, and ensure applications like Brother iPrint&Scan have permission to talk to devices on your local network. 
• Bypass the Shortcut App Conflict: Open the Mac Shortcuts app and look for any active or broken automated background tasks/triggers tied to scanning or printing; temporarily delete or disable them.
• Use Native Tools: If the Brother utility software crashes due to this background runner error, bypass it entirely by using Apple's built-in Image Capture app (found in Applications) to pull scans directly from your Brother hardware.