Mac Mail heading columns keep moving after updating to Big Sur 11.4

Hello,

I recently updated to Big Sur 11.4 and (Mac Mail v. 14.0) and now the heading columns in Mac Mail (From, Subject, Date, etc.) keep shifting and won't stay where I've always had them positioned.

The first attached image shows how the 'Date Received' column is shifted to the left.

The second image shows my normal setup with the "Date Received' column to the far right of the window.

The shift will occur if I do a search for an email or if I move to another folder, say the Trash, and then move back to the Inbox.

Sometimes, when I first open Mail, the columns will be shifted left - but not always.

Any suggestions on this new annoyance?

Thanks,

Joe