Angular ngx-bootstrap collapse is not animated

This could be a solution for the whole project.

.collapse {
    transition: all 0.3s ease-out;
    display: block !important;
    overflow: hidden !important;
    max-height: 0;
}

.collapse.in {
    transition: all 0.5s ease-in;
    max-height: 9999px; /*any number which is lager than a height of any of your elements*/
}

I had same issue and I resolve it by some css trick. It worked for me. I'm hoping that it would work for you. I happens because ngx-bootstrap doesn't use the ".collapsing" class so I done some changes in my code.

#your_nav{
    display: block !important;
    max-height: 1px !important;
    -moz-transition: all 0.3s ease-in-out;
    -o-transition: all 0.3s ease-in-out;
    -webkit-transition: all 0.3s ease-in-out;
    -ms-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
}
#your_nav.show{
    max-height: 230px !important;
}