Stacker tower extension cannot build due to collision with itself

I have three stackers that auto-placed their extensions but cannot build them due to the error message: "Cannot build: Collision with Stacker tower extension."
Removing and re-placing the extension results in a successful build.

I've rarely seen a blueprint that I could place but then had collision with something. The only other time was pretty recently while I was blueprinting a bridge.

Here's a save at the location of the above screenshot.

The bridge section I mentioned is also in the same save, at the bottom of the crater.

I can't reproduce this problem, did it happen at the same time for all 3-4 towers?

Yes, it did. It hasn't happened again, though.
I also haven't built any bridges since then

I have had the same thing happen to me. In my case, it seems to auto-resolve eventually but causes a big delay in the extension getting constructed.

is it possible that two ghosts have been created in the same spot, thus blocking eachother?

like normally when the user does so you cant double-place, even with blueprints as each ghost is checked one by one, but could it be specifically the automatic placement that for some reason under some condition it generates two instead of just one?

Fixed in the next patch.

seeing this happen on 0.8.5, if you manually place and unity-build extensions it can end up locked in a state where its trying to build extensions that already exist, and cannot proceed

and then apparently the "fix" is to build that doubled up section and then delete it when the stacker has moved onto it

hm