iPhone Mirroring screen is clipped and off-center on Mac after iOS 27 update

iPhone Mirroring on Tahoe with my iOS 27 iPhone works normally.

Have you rebooted your Mac? If not, that's the first step. If that does not help, then see if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, and also disables 3rd party extensions that may cause problems.

Start up your Mac in safe mode - Apple Support

If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.

Add a user or group on Mac - Apple Support

Once the testing is complete, the new account can easily be deleted.

Delete a user or group on Mac – Apple Support

Those steps will help to isolate the problem.

It might help to download and run EtreCheck, written by a long-time forum member. The free version is fine. Post the full report using the Additional Text button. No personal information is revealed. 

Well, I'd suggest upgrading your Mac to macOS 27, but iPhone Mirroring is misbehaving there, even worse. Here, you can see by the mouse pointer that I clicked on the Starbucks app...but what's opening is actually the calculator app, which is one row up and two columns to the left of where I clicked.

Sheesh.

It's clearly a software bug, not sure any help for users trying these time consuming steps will isolate where the issue is unless users can see source code or detailed system log. You mentioned you had the similar issue before updating to iOS 27. Have you tried any of the steps you mentioned? What's the result?

Same issue, but with Mac OS Sequoia 15.8. Seems iPhone mirror is crippled on iOS 27? Mind boggling that Apple didn't do any testing that a simple smoke test gonna show this sev2 bug