Magura Vyron dropper seatpost internal shaft can be easily twisted
Something similar happened to me a couple of years ago, after my bicycle was transported by a freight company for several thousands of kilometers, and the Vyron seatpost apparently had received a couple of sideways strikes.

You do not provide details about which seatpost's parts are loose. I'd guess it is the internal movable shaft that now rotates against the external piece. It seems (at least it was so in my case) that the shaft of the seatpost is threaded into something inside. It means you can thread it back to be tight by rotating the shaft clockwise (looking from the top). Be careful to not unscrew it all the way out of course, it should get tighter quite soon after you start rotating it.