Hi Daniel5926,
We'd like to share a suggestion to help you with the back button not working. We would recommend starting with making sure the macOS is on the latest update via Update macOS on Mac
"Use Software Update
Before installing new software, it's a good idea to back up your Mac.
To check for new software, open Software Update. It's in System Settings (or System Preferences), which you can open from the Apple menu in the corner of your screen:
- Choose Apple menu > System Settings. Click General on the left side of the System Settings window, then click Software Update on the right.
- Or choose Apple menu > System Preferences, then click Software Update.
If Software Update finds new software, click the button to install it, then enter your administrator password when prompted. During installation, your Mac might show a progress bar or blank screen several times, and you should avoid putting it to sleep or closing its lid.
If Software Update says that your Mac is up to date, then no new software is currently available for your Mac model. Software Update shows only software that is compatible with your Mac."
This will ensure this would not be an issue with macOS. If this issue remains, you'll want to contact Apple Support so this can be further investigation due to this unexpected behavior: Get Support
Thanks for using Apple Support Communities.