I just happened to be in the dev kit when I saw this one. So I was able to reproduce this error in the current version of the game too, though I may have spotted something you didn’t (or at least is apparent in live but not testlive).
Here we have our lovely building, 2 pillars with a wedge.
The upgrade is complete, however it didn’t replace the wedge, the two pieces merged together instead. I used black ice as an example to try and make it more visible, but I tested it with other tiers and versions as well.
When the wedge isn’t in-between two pillars, it works like normal when upgrading. A normal square ceiling that is in-between two pillars also upgrades correctly.
Walkway should be against the wall, Doorframe where my clanmate is.
We can’t walk on the walkway crossing the room, we can walk where it should be but it is not now.
Also holes in the wall.
EDIT:
If I upgrade the piece where it should be (and I can) the upgrade piece is in the correct place.
The upgraded piece crumbles at the wrong place.
I wonder if seeing clan members on the map could be glitched by players to find others outside their clan, I hope it never happens because this could be catastrophic for the game.