As many PC users know, the connectivity to the game is flawed to the point of people quitting Trials all together. I personally always find myself lagging out when I'm on 4-6 wins with no losses and having myself or a teammate DCing. I suggest if you DC you can't change your gear and you can join back unless you forfeit your position e.g. "Hold F To Leave" so then you can continue with your day.
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I can understand not letting you join mid game, but it should let you join back after each round.