Quick answer: Enable Y Sort Enabled on the TileMap layer and on the characters' parent, set the tiles' y-sort origin, and keep movable sprites and the tilemap under one y-sorted node.
Y-sort that does not order sprites correctly usually has y-sorting disabled somewhere or a missing common parent. Here is how to set it up.
How to fix it
1. Enable y-sort on the layer and parent
Turn on Y Sort Enabled for the TileMap layer and for the node that parents both the tilemap and the characters, so they are sorted together by their vertical position.
2. Set the tile y-sort origin
Tiles need a y-sort origin set in the TileSet so the engine knows where their visual base is. Without it, tiles sort by the wrong point and overlap incorrectly.
3. Keep movers and tiles under one y-sorted node
Characters and the tilemap must share a y-sorted parent to sort against each other. If they are in separate, unsorted branches, their overlap order will not be computed together.
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 Godot 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.
Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.