Quick answer: Define sockets with a consistent forward axis and snap each module so its connecting socket exactly matches the mating socket's transform, on a fixed grid so dimensions always line up.
Modular level kits look broken when corridors do not meet their doorways. Standardizing socket transforms and grid units makes every connection flush.
How to fix it
1. Standardize socket orientation
Define every connection socket with a consistent outward-facing axis (e.g. local +Z points out of the module). To connect, rotate the new module so its socket faces opposite the existing one, then translate so the socket origins coincide.
2. Author on a fixed grid
Build all modules to a common grid unit so a doorway is always the same width and at the same offset. Mismatched authoring dimensions are the most common cause of a gap that no amount of snapping fixes.
3. Snap to the connector, not the pivot
Compute the connection transform from the socket's world transform, not the module's root pivot. Modules whose art is offset from their pivot will misalign if you snap by the root.
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 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.
Most of the time the fix is small. Seeing the failure clearly is the part that actually costs you.