With my Canon 1ds Mk III, often (but not always), the thumbnail in Bridge does not reflect the changes made in ACR. For example, if I increase the Brightness, the thumbnail might not appear lighter.
If I crop left-right, the thumnail will show the crop, but the thumbnail is moderately distorted.
Both of these problems are with the thumbnail only. Once reopened in ACR, only then can I confirm that I have lightened the image. That's a pain, having to open many images just to see if I have made the change. Strange that it only happens about 40% of the time.