White rectangle in the middle of my screen

Judil wrote:

I have a Macbook Air from 2014. I don't have a Macbook Pro.

A white rectangle comes up in the middle of my screen. If I restart the computer, it comes back, though not straight away.

On a previous similar query, this was solved by disabling Firefox. I don't have Firefox. I use Safari and occasionally Google Chrome.

Can anyone help?

Thanks.

Judi

— Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc. Login and test. Reboot and test as caches get rebuilt.

In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.

This will tell you if third party interference; extensions etc are not loaded in safe boot mode.

— Test issue in another user (or guest user) account  https://support.apple.com/en-us/HT204443

This will tell you if it a universal issue or isolated to your user/admin account.