Yes, correct. When changing from typically sheet 1 to sheet 2, Excel automatically opens a new file with a copy of just sheet 2, leaving me with two files open, both open at sheet 2.
Yes, quite correct, the Formula bar was open just above the worksheet
tabs at the bottom.
I closed the Formula bar, and then toggled between sheets and no new workbook opened.
Simple answer, but you thankfully solved a very annoying problem.