This pretty much speaks for itself.
I was testing out some custom thing scenery for my level pack revival whatsit, and, for some reason, each and every one of the things were buried underground. (Notice how the big fern clips behind the grass thing despite being in front of it.)
First attempt, replacing the mario bushes: underground things. Second attempt, using freeslots: still underground things.
I even tried putting them a little bit above the ground, but they just fell right back into the positions shown in the screenshot!
I have literally no idea why it does this, so some help would be greatly appreciated.