If they have any neighbors counted (more than 1) then the Zwave SDK on the Hub will refuse to remove them and always says it is no longer on the failed node list. The only way to remove those is with a USB Zwave stick and PC Controller, or to get the neighbor count down to only the hub.
I am curious, do all of yours that are stuck have more than 1 neighbor?
The neighbors number is blank? Odd I would think those would be removable from the hub.
I suspect all the ones you could remove were showing only 1 neighbor (I do not expect you to specifically remember this however).