What happens if you delete below lines responsible for sidenav only?

<link href="{{ url_for('static', path='/mdb/css/modules/sidenav.min.css') }}" rel="stylesheet">
<script type="text/javascript" src="{{ url_for('static', path='mdb/js/modules/sidenav.min.js') }}">

Try running your project only on mdb.min.js and mdb.min.css imports. How does the sidenav behave?

Hi Michał,

It seems the "mdb.min.js" is the issue, as soon I remove it the sidebar works fine.

However I still need the 'mdb.min.js' as my modals stop working:

<script type="text/javascript" src="{{ url_for('static', path='mdb/js/mdb.min.js') }}"></script>

Any ideas why it is conflicting?

Hello, it should be enough. Your paths may be leading to unexisting files. Do you experience errors in the console? Is anything of above throwing 404? Could you provide the exact code that you used in your project? You can recreate it in snippets: https://mdbootstrap.com/snippets/