Tank mastery 50 skin

So I've finally got my main battle tank mastery level 50 applied the skin and the armour is far worse than a stock tank, only 2 hits at the front will destroy the tank, I've tested it multiple times with different variants but still with the same result, Originally thought it was me but other players who have got the mastery 50 have noticed it and no longer use the level 50 tank as its simply useless on the battlefield  so we have had to go back and use stock tanks.