Quick answer: Define named socket transforms on each piece, find the nearest compatible socket, and align the wall's matching socket to it rather than guessing offsets from bounds.
Walls almost line up with a foundation but sit a few centimeters proud, or snap to the opposite edge entirely. This happens when snapping is derived from bounding-box math instead of explicit sockets.
How to fix it
1. Author sockets as child transforms
Add empty child transforms at each connectable edge of the foundation and at the base of the wall. Tag them with a type like WallEdge so only compatible sockets pair up.
2. Snap socket-to-socket
Find the nearest foundation socket to the cursor, then position the wall so its own socket transform coincides with that socket, matching rotation. This stays correct even when the foundation is rotated.
3. Validate before commit
Reject the placement if no compatible socket is within the snap radius, so walls cannot be dropped a hair off the edge in free-placement mode.
Catching the ones you can't reproduce
The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.
Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.
This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.
The errors you never hear about are the ones quietly costing you players. Visibility turns them into a worklist.