Mornin All, burning the midnight oil here

I've got some strange behaviour with a series of linear patterns of extruded cuts.  I have 2 bodies, which I copied and combined the copies.  So that's 3 bodies total, with one of them just being equivalent to the sum of the other two.

I am using All Bodies as the feature scope

Just one of my pattern instances fails on just the combined body.

Here's a close up of what it should be

and here's the ugly result on the combined body

Really don't know what is happening here, it's been working for hours..

the especially weird thing is that it works perfectly on the original but only partially on the copy

problem body set transparent

There is no error or warning in the tree, but it's made a right mess of me tenon :/