The lateral play is a well known issue with the original Joplin (the 3" version) but it is purportedly cured by the Joplin 4. The original used one slotted bush while the new one uses two.
In fairness the play does not stop if from working, although it can get so bad at to be quite disconcerting.
There is nothing you can do to fix it other than ask the retailer/distributor to swap it for a Joplin 4, which I know they are doing.
They are all flawed, perhaps until the Rock Shox Reverb comes out, but they are still worth every penny and every moment of hassle IME.