Loosing references to objects inside containers

I am struggling fixing a piece of code, even though I believe I know the cause. I did search a lot on Stack Overflow and many people had similar issues (and good answers were provided), but still, I am not sure I understand the problem with my code. I tried giving a smaller example, but the structure I have is not simple by itself. I hope the following is simple enough.

My objective on the excerpt:

• Have a vector of points.

• Have a vector of segments. (Whose endpoints are reference to points in the vector above)

• Have a vector of events. (That keep a reference to the exhisting segments and points)

segment::segment (point &pt1, point&pt2, int i) {
   s = &pt1; e = &pt2; ind = i; // point *s, point *e, int ind
}
event::event (segment &s, point &pt, int tp) {
   seg = &s; type = tp; p = &pt; //segment *seg, int type, point *p
}
void pre_process (int size, std::vector<point>& pts, std::vector<event>& evts,
        std::vector<segment>& segs) {
    float x, y;
    for (int i = 0; i < size; ++ i) {
        std::cin >> x >> y;
        pts.push_back({x,y});
    }
    for (int i = 0; i < size; ++i) {
        int j = (i+1)%size;
        if (cmpXY(pts[i], pts[j]))
            segs.push_back({pts[i], pts[j], i});
        else
            segs.push_back({pts[j], pts[i], i});
        evts.push_back({segs[i], *segs[i].s, 0});
        evts.push_back({segs[i], *segs[i].e, 1});
        std::cout << 2*i << "\n";
        std::cout << segs[i].s << "\n";       //ALWAYS EQUAl
        std::cout << evts[2*i].seg->s << "\n";
    } // LINE X
    for (int i = 0; i < size; ++i) { //LINE Y
        std::cout << 2*i << "\n";
        std::cout << segs[i].s << "\n";        //DIFFERENT SOMETIMES
        std::cout << evts[2*i].seg->s << "\n";
    }

So, the problem is that some of addressess my objects are pointing to change from LINE X to LINE Y. In particular, pts and segs remain the same.

From what I know and from what I understood here or here I cannot get the refeerence to an object on the stack of any function (my for loop, for example). However, I believe the lifetime of the object on the container is the same as the container itself. It makes me believe that all objects I push_back() should persist through the funtion pre_proccess and the function that is calling it.