jank in mixed bodies physics example (Firefox only)

Version

• Phaser Version: https://phaser.io/examples/v3.85.0/physics/matterjs/view/mixed-bodies
• Operating system: MacOS 15.4.1 (24E263)
• Browser: Firefox 140.0.4

Description

If I grab one of the objects in this example and drag it around quickly, I can trigger a 1.5s freeze. In Chrome, I can't reproduce this hitch, but I notice that I have fewer objects left on screen after shaking for a while, so it's possible that the moment something first levels the visible part of the scene is related to when the slowdown happens.

Edit: I believe the hitch happens whenever something is pushed off-screen; once recognizing this, I was first able to reproduce two perf hitches in the same session (without refreshing or changing tabs)

Example Test Code

https://phaser.io/examples/v3.85.0/physics/matterjs/view/mixed-bodies

Additional Information

A normal perf trace

A trace for the "jank" moment as labelled by the devtools debugger :-)

Start with the mixed-bodies Matter physics example at the linked Phaser example URL and reproduce the hitch in Firefox while dragging bodies quickly, especially as objects leave the visible scene. Compare a performance trace with Chrome and Firefox; done means the reproducible freeze is eliminated without introducing the reported object-loss behavior.