What causes GameMaker chain links separating under tension?

The revolute or distance joints connecting the links are too soft and Box2D runs too few solver iterations for the long constraint chain, so heavy tension stretches the gaps until links visibly separate.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix GameMaker Chain Links Separating Under Tension

Quick answer: Use stiff joints between links, keep link mass ratios reasonable, and avoid hanging a very heavy body off light links, so the chain holds together under load.

A hanging GameMaker chain whose links pull apart into floating gaps when a heavy body is attached has joints that are too soft for the load and a solver that cannot fully converge the long chain. Here is how to fix it.

How to fix it

1. Connect links with stiff joints

Join adjacent links with revolute or distance joints created via physics_joint_revolute_create; keep them rigid (no excess slack) so each link stays anchored to its neighbor under tension.

2. Keep mass ratios sane

Avoid attaching a very heavy object to very light links; large mass ratios are hard for Box2D and force the links apart. Give links comparable density or cap the hanging load.

3. Shorten the chain or add support

Long chains accumulate more stretch per step than short ones. Use fewer, heavier links where possible, or anchor the chain at both ends so tension does not pile onto one weak link.

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 GameMaker 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.