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 a GameMaker Physics Joint Exploding When Bodies Spawn Overlapping

Q: What causes a GameMaker physics joint exploding when bodies spawn overlapping?

Creating a revolute or distance joint between two fixtures that already interpenetrate makes Box2D apply large separation impulses on the first step, throwing the bodies apart.

Quick answer: Spawn the bodies separated, create the joint at their resting offset, and limit the world's velocity or step the world once before enabling collisions.

Two objects joined with physics_joint_revolute_create fling apart the instant they appear. They spawn overlapping, so the solver depenetrates them violently. Placing them at the correct separation before joining stops the blowout.

How to fix it

1. Spawn bodies non-overlapping

Position the two instances at their intended joint separation before calling physics_joint_*_create, so the fixtures are not interpenetrating when the joint is established.

2. Disable collision between joined bodies

Pass collide-connected as false (or put them in non-colliding groups) so the joint does not also have to resolve a fixture overlap between the connected bodies.

3. Limit initial velocity

Cap phy_speed or zero the bodies' velocities for the first step after creation so any residual depenetration impulse cannot accelerate them off-screen.

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.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.