For prominence you have to look AROUND the summit, not just in one direction.
Following the 850 meter contour line you will see that there are several higher peaks inside the 850 contour. A few examples are Fichtelberg, Klínovec, Plešivec and Blatenský vrch . For the exact heights I am not sure. It could well be that Germany and Czech Republic use a different reference.
73, Hans PB2T