I received the JJ2A3-40 about a month ago, ordered from Eurotubes, but with two different glass envelopes. One with a larger envelope, ceramic base with the logo on the glass, the other one is smaller with bakelite base and the logo on it. Michael of Eurotubes told me that the one with the smaller glass envelope is the new product. And he sent me a replacement direct from JJ in Slovakia, it arrived last week Saturday, with the same specification as the one already with me. Michael also told me that the 6 months warranty starts at the day I receive the replacement tube, which is very fair of them. And I don't have to send the old type back to them.
I must say that the Eurotubes is very responsible and act promptly. Maybe there are some JJ products that came from a bad batch, but with their service I won't hesitate to buy the JJ products from them again.