If you got two collision bodies, you got two options to set collision_mask. Lets say we got Player on Layer 1 and Ball on Layer 2. Now you can either set on both collision the equivalent masks or just at one of those.
In my case if i set the mask just at one of them, the behavior is different - its like the physics doesnt work corrently.
Have you experienced the same or how is it supposed to be?
(docs)
If you have one object on Layer 1 with collision mask 1, and the other one on Layer 2 with collision mask 1, bad things will happen because one object collides with the other but not the other way around. This would never occur in real life and I don’t think it’s desirable in a video game either. If you want proper collisions, set both layers and masks so that they can collide with each other. (e.g. Layer 1, collision mask 2; Layer 2, collision mask 1)