It was with Stans sealant admittedly, i’ve bought a new tube and fitted it with the Schwalbe blue dot fluid this time. I can’t imagine it makes any difference.
Also, the sealant migrates to the outer chamber filling holes on the valve and gets into the tube/valve assembly. this then blocks the top of the valve making it a pain to adjust pressures and deflate the tyre. literally took 10 minutes to empty the tyre to the point i could pop the bead seat.
to sum up, it offers game changing performance, but it is flawed and very very expensive (spare tubes are £25..). If you can deal with the quirks and the cost, it is totally worth it. If you want hassle free… maybe not.
and as a side note, also mentioned above, the tyre levers are absolutely ace!