Hey boidarkly,
You could see if turning off Universal Control, restarting your devices, and turning that back on may help allow you to rearrange the displays as you'd like. It may seem like a simple step, but restarting your devices can help resolve unexpected issues.
Another step you can try is to see if the same issue happens in a temporary test user. A test user doesn't have custom or changed settings, so that can help show if the issue is specifically happening in your current user or any user on your MacBook Pro. That can start help isolating what might be going on. If needed, the steps below show how to create one:
- Open the Apple menu > System Preferences
- Choose Users & Groups, then choose the padlock in the lower left-hand corner to unlock it to allow changes
- Click the + icon right above the padlock and create a new temporary administrator user
If needed, you can read more here: Set up users, guests, and groups on Mac
Let us know how those steps go.
Take care!