menu sub items don’t collapse

Hello there,

I have read several posts with this issue, but did not manage to fix it for my site. The problem probably started after the last update to 1.6.6.

I don’t have a child theme, neither custom css, and I couldn’t find any .main-navigation definitions in the style.css file.
I did find some .main-navigation definitions in the rtl.php file (the site is in hebrew) but I don’t know what to change to make it work.

.main-navigation {
    float: left;
}

.main-navigation li {
    float: right;
    padding: 0 25px 0 0;
}

.main-navigation a {
    float: right;
}

.main-navigation ul li ul {
    right: 25px;
}

.main-navigation ul li ul li ul {
    right: 150px;
}

.site-header .menu-toggle:before {
    margin-left: 10px;
}

.main-small-navigation ul ul a {
    padding-right: 60px;
}

.main-small-navigation ul ul ul a {
    padding-right: 80px;
}

.small-menu {
    float: left;
}

.small-menu li {
    float: right;
}

.small-menu a {
    float: right;
    padding: 5px 16px 0 0;
}

Many thanks!

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