BGA Issue

We are in process of building a product which is a double sided board ( SMT ) and PTH ( topside ). This particular product has a BGA on the topside of the board, which has a kind of plated top on the die. I have heard some companies have had a problem of potential re-reflow of the BGA bumps when the board goes over the wave during bottomside soldering. We also mask the topside of the vias in the BGA area. If any of you have seen such problems, I would like to share your experiences. Thanks in advance

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