I don't think there would be any real balance issue but you could always take the last insert out of every row to maintain balance if the machine showed excess vibration with one insert removed. I guess it depends on how important it is to get back to work vs. waiting for screws to arrive.
That is also true and obvious. Didn't think of it. I would have done that too. Guess my mind was blown (a) with the broken insert and (b) the fact that it might be the one I removed and didn't put it back on correctly.