Why climbs mobile menu when the resolution from 768 to 991? how to fix?

verstka.vetov.ru/yunika/index.html
If presititi the browser window, you can see that the resolution from 768 to 991 mobile menu appears.
And must be from 768 only.
Can't understand where messed up(
June 8th 19 at 17:00
2 answers
June 8th 19 at 17:02
bootstrap.css:
.collapse {
 display: none;
}
...
@media (min-width: 992px) {
...
 .navbar-collapse.collapse {
 display: block !important;
...
}
}
June 8th 19 at 17:04
the question is removed

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