I had issues with the rear Thunderbolt 5 ports on my (new) Mac Mini M4 Pro. I connected my older/wired Apple Keyboard, via Apple’s own USB-C to USB-A adapter. While my Apple keyboard worked (without any issues) for a number of hours, it stopped working the following day. The problem was isolated to all of the rear ports - no issues with the front ports. When I mentioned my difficulties with an Apple employee, I was told they had to replace the rear port on another client’s system (experiencing similar problems). I was advised to arrange a consult with a technician (Genius Bar). Not wanting to crack-open a brand new system, and fearing other potential issues, I simply returned my machine for a refund. I will wait until this seemingly common issue is resolved before trying again. Unfortunate.