The first time page is loaded when i point my mouse over a link it starts to quickly change its size and/or its font-weight several times (like shaking), how it looks is here: https://youtu.be/kaEapSLiHAQ. I thought maybe it's my browser (using Waterfox) but same occurs in Chrome too. I use VS Code with Live Server plugin so may it be Live Server's bug? May transition cause it? If so, how do I fix it?
.header {
    display       : flex;
    flex-direction: column;
    align-items   : center;
}
.top-menu {
    display        : flex;
    list-style-type: none;
    border-bottom  : 1px solid rgba(0, 0, 0, .3);
}
.top-menu a {
    text-decoration: none;
    color          : #113453;
    padding        : 1em 1em .5em 1em;
    display        : block;
    transition     : color .5s;
    transition     : font-weight 1s;
    font-family    : 'Cormorant Unicase', serif;
    font-weight    : 300;
    margin         : 0 .1em;
    position       : relative;
    
}
.top-menu a:hover {
    color      : #404435;
    font-weight: 700;
}<body class="page-content">
    <header>
        <nav class="header">
            
            <ul class="top-menu">
                <li><a href="#">О студии</a></li>
                <li><a href="#">Услуги</a></li>
                <li><a href="#">Вопрос-ответ</a></li>
            </ul>
        </nav>
    </header>
</body> 
    