The very early Mark1s made mid 2004 had a firing valve that the manufacturers would replace under warranty if the owner reported problems; it wasn't actually a product recall.
Some also had the threads for the air tube badly made at the reg housing, and this caused misalignment problems between the air tube and the barrel, which wouldn't have been too much were it not for the figure of 8 clamp at the front which tried to hold them parallel. It was a known problem with one batch. Two of us in this region had the same issues of POI shift and we both had the same free-of-charge fix.
Floating the mark 1 barrel was not a good solution either.