As you indicate, there is probably some problem with the particular screws. It might happen that tehy bend slighty, I don't think that in itself is an indication of a faulty batch.
It's not a very easy job to remove the, I had it happen on a custom board not long ago and managed to drill it out and remove most of the screw, at least enough to get a new one in there. But it is difficult work because you risk drilling through the plug and it takes some precision to drill in the middle of a steel bolt, not slipping sideway into soft plastic. The other option is to simply replace the insert, which is a very easy job for a professional.
But you ask about warranty. I can not say if this is covered or not. And in any case warranties always goes through the retailer. SO my advice it to contact the shop where you bought the board and see what they say.
I have one maybe far fetched hypothyses about this. Its about the supplied screw driver. The fit in the screw is so good that if you are not holding the screwdriver perfectly aligned with the bolt, the misalignment might actually create a slight bending of the screwhead. And when you push down and twist, this will indue a spiraling motion of the whole head. That could maybe be enough to weaken the screw considerably. This may not at all be what has happened, but in any case to be better safe than sorry my advice is to be careful with screwdriver alignement when mounting the footstrap screws.