Quick answer: GameMaker physics_fixture_create crashing when mass = 0? Zero-mass dynamic bodies are undefined - use kinematic body or set mass to small positive value.

Created a sensor with mass 0 expecting it to ignore gravity. Game crashed with no error message.

Use kinematic body

physics_apply_force(..., 0, 0)
body.kinematic = true

Kinematic bodies ignore physics forces; valid mass not needed.

Or use small positive mass

Mass 0.001 behaves nearly weightless without the zero-mass crash.

Use sensor flag for triggers

physics_fixture_set_sensor(true) creates a non-colliding trigger volume. The right primitive for the use case.

“Physics bodies have rules. Zero mass violates them.”

If your physics setup has zero-mass bodies, replace them with sensors or kinematic. The crash is a warning sign about misuse.