One of the 5 nuts rotates (with the use of the socket so we are not talking loose) with the thread ie the nut does not come undone but neither can it be tightened up fully,
I wouldn't say it's normal then, but I doubt it would cause you any major problems for now, check your eccentric hub though to make sure it isn't or hasn't backed up and has started wearing the adjustment out.
When taking the cush drive nuts off you need to put a large hex key behind the cush drive to keep it still. Whether this means that the cush drive is worn or not I do not know. It was a while ago I did it. As I recall you need to be careful of the swing arm and ensure the key does not grate on it.