Hi David, one of your cutout pieces seems to have a couple of extraneous little tiny micro curves pieces overlapping on top of the main piece. I found them by selecting all the big pieces and then doing a Select > Invert which then displayed "2 curves selected", and turning on their control points shows that there are 2 micro curves here:



So something is a bit odd with at least one of those cutting pieces - it's got some kind of little overlap or mis-alignment thing in it as well. I'll see if I can find which one is the bad one.

But anyway, that's why Burr's method of picking one of them and redoing the circular array works, because that got rid of the bad cutting piece and replicated a good one into its place instead.

Also one note - the booleans know how to use a planar curve as a cutting object directly, so you don't actually need to do extrusions as a separate step if you want to cut a hole all the way through the object, just pick the curves as the cutting objects directly and the booleans will internally extrude them for you. So that also means that if you do make extrusions you want to make sure to avoid selecting the curves also as cutting objects or else you'll be telling the booleans to try and cut those areas twice.

- Michael