Need help with iter_combinations

[Almazoioio]

`fn Step(
mut query: Query<&mut Ball>,
win: Single<&mut Window>,
) {
// Get the window dimensions
let res = win.resolution.clone();
let mut vx: f32;
let mut vy: f32;
let mut vx2: f32;
let mut vy2: f32;
let mut d: f32;
let mut dot: f32;
let mut query = query.iter_combinations_mut();

// Physics step
while let Some([mut ball, mut ball2]) =
    query.fetch_next()
{
    // Gravity acceleration
    ball.speed.y -= gPerStep;
    ball2.speed.y -= gPerStep;

    // Update the position by its speed
    vx = ball.pos.x + ball.speed.x;
    vy = ball.pos.y + ball.speed.y;

    vx2 = ball2.pos.x + ball2.speed.x;
    vy2 = ball2.pos.y + ball2.speed.y;

    d = (ball.pos - ball2.pos).length_squared();
    
    if d < dim * dim {
        // d = d.sqrt();

        // Calculate the normal and tangent vectors
        let normal = (ball.pos - ball2.pos).normalize();
        let tangent = Vec2::new(-normal.y, normal.x);

        // Decompose the velocities into normal and tangent components
        let v1n = normal.dot(ball.speed);
        let v1t = tangent.dot(ball.speed);
        let v2n = normal.dot(ball2.speed);
        let v2t = tangent.dot(ball2.speed);

        // Calculate the new normal velocities using 1D elastic collision equations
        let v1n_new = v2n;
        let v2n_new = v1n;

        // Convert the scalar normal and tangent velocities into vectors
        let v1n_new_vec = v1n_new * normal;
        let v1t_new_vec = v1t * tangent;
        let v2n_new_vec = v2n_new * normal;
        let v2t_new_vec = v2t * tangent;

        // Update the velocities
        ball.speed = v1n_new_vec + v1t_new_vec;
        ball2.speed = v2n_new_vec + v2t_new_vec;
        
    }




    // Check for window bounds
    if vy.abs() > res.height() / 2.0 { ball.speed.y = -ball.speed.y; }
    else { ball.pos.y = vy; }

    if vx.abs() > res.width() / 2.0 { ball.speed.x = -ball.speed.x; }
    else { ball.pos.x = vx; }

    if vy2.abs() > res.height() / 2.0 { ball2.speed.y = -ball2.speed.y; }
    else { ball.pos.y = vy; }

    if vx2.abs() > res.width() / 2.0 { ball2.speed.x = -ball2.speed.x; }
    else { ball.pos.x = vx; }
}

}`

Hello! I'm struggling with iter_combinations:
For some reason when I'm running my program I'm having an issue with physics: every ball is having defferent ticking rate and as a result one of them is not being processed, others having defferent insance processing speeds, and only one is having normal processing speed

I've at first tried to use nested loops, but borrower haven't allowed it

I can't figure out what I'm doing wrong.

Violet = no updates
Red = way more updates
Blue = right amount of updates

[Almazoioio]

Fixed:
Separating collision and physics systems