SlickNav plugin no working on mobile

Question

I am using slicknav plugin for menu and it works great on desktop an ipad. On cell phone, while scrolling through the menu or clicking anywhere outside the menu, closes the menu.

My code:

<li> Item 1
    <ul>
        <li> sub-Item 1</li>
        <li> sub-Item 2</li>
        <li> sub-Item 3</li>
    </ul>
</li>
<li> Item 2
    <ul>
        <li> sub-Item 1</li>
        <ul>
            <li>sub sub item 1</li>
        </ul>
        <li> sub-Item 2</li>
        <li> sub-Item 3</li>
   </ul>
</li>
<li> Item 3
    <ul>
        <li> sub-Item 1</li>
        <ul>
            <li>sub sub item 1</li>
        </ul>
        <li> sub-Item 2</li>
        <li> sub-Item 3</li>
    </ul>
</li>
<li> Item 4
    <ul>
        <li> sub-Item 41</li>
        <ul>
            <li>sub sub item 1</li>
        </ul>
        <li> sub-Item 42</li>
        <li> sub-Item 43</li>
    </ul>
</li>

If I click on menu on cell phone and then scroll to sub-items 41 or 42.. the menu closes. I want the menu to remain open.

Thank You in advance for help.