How to Fix a Godot Idle Bob Tween That Drifts the Object Off Position Over Time

An idle floating coin or character slowly slides off its spot after looping for a while. The bob is built from relative moves that never perfectly cancel. Bobbing relative to a fixed stored origin removes the drift entirely.

How to fix it

1. Store the origin once

Capture the base position in _ready() and tween between origin + up and origin - down as absolute targets so the midpoint never moves.

2. Or drive it from sine of time

Set position.y = origin.y + sin(time * speed) * amplitude in _process(delta). A pure function of time cannot accumulate drift the way chained relative tweens do.

3. Avoid as_relative for loops

Reserve set_as_relative() for one-shot nudges; for endless loops it compounds rounding error each cycle and walks the object off its anchor.

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.