Well, you called it "the large dial" in some of the posts above, and specifically the "large rear dial" in one of them. Thus I assume you mean the dial beside the display on the rear, the one Canon calls "quick dial", since while looking at it, it's much larger than the small part you can see of the dial behind the shutter button. That's the one Canon refers to as the "main dial".
But if you actually mean the front dial, just behind the shutter button, then I rest my case. There's no programming which will make that an ISO dial nor any exposure compensation dial, unless you first press the ISO or +/- buttons on top, respectively.
If you want to, and I was not confused about which dial you referred to, you can try this, on your now well behaving 1DX Mark II.
- Press MENU.
- Go to Custom functions group.
- Roll to the C.Fn6 page.
- Select the fifth item from top.
- Select the fifth item from top in the right column.
- Select the sixth setting (just before OFF).
- Press SET.
Half-press the shutter button and then use the +/- and ISO buttons on top, as well as the dial on the rear, and check if the camera now behaves as the faulty one.
Sorry I didn't notice your first call for help here. These "model XYZ owners" threads are so full of pictures, that all questions about the camera itself disappears in noise. I recommend starting a separate thread for actual issues, since wading through the posts here to notice such questions isn't too efficient.