Since the slider was redesigned, should you really proceed to a new final production mold or do a test first to make sure the redesign really works correctly? I also do not understand why the manufacturer will not correct the tolerance level to match what was originally agreed. They were the one's than changed it to an incorrect value. If you redesign the mold, then the entire cost is on the person redesigning. I am not trying to be critical here, just making observations. I am really surprised the manu could screw up the tolerance and not make good on it. Especially considering the only value American manufacturing has is to get the job done right, since we know it won't be cheap. If an injection mold leaves a rough spot on the slider, I can file it... it's not that big of a deal since I will be filing the top housings anyway. Hopefully things will work out.
They are willing to fix the issue at their cost, but are charging to machine geometry they will have to machine already, in order to fix their mistake, in order to update the mold. It is hard to explain really but basically they have to fill up the messed up area with material via welding, and that will fill up areas that don't need material, because the part is so small and welding is not precise enough. This means they have to machine the affected areas again, and my updates happen to be areas that are affected areas from the repair. It doesn't make sense for me to pay full price for the fix, if they are already machining those areas, as it actually doesn't cost them any extra, they are more just offloading the lost profit back onto me. It like getting a cake that has the wrong flavor on a layer, and asking to get the frosting changed partially when they do it, and being told that you have to pay for that change even though they are putting new frosting on anyways. Weird analogy, but it was the only thing that I could think of that may help a bit more in getting my point across.
There will not be any defect on the sliders, they just entirely machined out geometry, that I designed in, for no reason...The updates just make the final product near perfect, so that the early adopters don't get shafted with crappy parts.