On macbook pro/ Sonoma, Mail app window goes blank after a moment.

Here's what happens more accurately. I highlight an email in Mail. A second window opens for that email, on top of the main inbox window, showing the opened email message. After about 16 seconds the message window goes blank. It doesn't stay open long enough to read a long message, and clicking on upper left red dot doesn't close the blank window. I can click on the Inbox window which is still open, and re-open the same message. Same result, it goes blank in about a quarter of a minute. I attached a photo of the message window after it goes blank after opening 3 times. It's definitely not working as it should.

Is no one else experiencing this?