Faces missing after using trim function

After using the trim function in the way seen below I keep getting faces where I don’t want them and I am missing some faces where I do want them (sometimes). It seems like every other time I get the faces but I end up with a situation like picture 2. I have been working on this for a while but I haven’t had much success. My model units are in mm but I am using the default inches and planning on scaling it back down later.

example.skp (104.8 KB)

The middle shot looks like there are 2 coincident faces. (I see z-fighting.)

Looking at the first GIF, I wonder if the boolean subtract method would be better than trim ?

I got the same result with subtract. I’m still trying to figure this one out. It appears as if there is a infinitesimal difference in the z value at the bottom. It’s strange though because all my values are in inches.

Make sure there are no stray edges. And look for tiny edge lengths.

stray edges meaning? The skp is attached to the first post if you would like to see it yourself. I think this is just an issue where sketchup’s position assignment isn’t necessarily accurate.