I regret to say that I'm not surprised. The cells are usually very good, but LifeBatt as a company seems to be a bit variable, in particular the chap that owns it/set it up, Don Harmon, has gained a reputation here for being somewhat of a nuisance (in fact I think he was, at one time, banned from here).
Michelle Robinson also has a bit of a hard reputation, I gather, so I doubt that they will provide you with the new cells you need. It seems very likely, looking at your photos, that they fitted two cells from a different batch, perhaps even of a different standard, to your pack and it is those cells that have failed. It would seem to me that the problem was almost certainly faulty cells, and these are now causing the BMS in the pack to trip out.
Jozzer may know where you can get two new cells in Europe, as he used LifeBatt cells and I believe knows more about the company and their products. LifeBatt also had a UK agent, a chap called Ian someone, who might be able to help, assuming he's still selling LifeBatt.
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.