Shimano XT Cassette, Loose ring

[Sidmouth]

I have 2 of these on each wheel set, I have noticed the 4 ring from the top is loose, like the rivets are not holding that ring solidly and there is a very slight bit of play, which I'm sure will increase, there can not be more that 1000km on each, is this normal and is it ok to ride and for how long.

 

If this has happened to both cassettes im sure its a common thing