Stack Overflow questions/answers similar this one did not work for me.
Browser window reduces width until drop down tabs are replaced with hamburger symbol, which opens on a click to expose menus. The problem is the hamburger symbol needs a second click to collapse, instead of collapsing on clicking one of the exposed menus.
This problem has been reported before. None of the suggested scripts worked. The suggested solution (5) using data-target=".navbar-collapse"
in each dropdown nav link succeeded in collapsing the hamburger symbol as intended, but stopped the menus working.
<nav class="navbar fixed-top navbar-expand-lg navbar-dark bg-secondary">
<a class="navbar-brand" href="#"></a>
<button class="navbar-toggler" type="button" data-toggle="collapse"
data-target="#navbarSupportedContent1" aria-
controls="navbarSupportedContent1" aria-expanded="false" aria-
label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent1">
<ul class="navbar-nav mr-auto">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown 1" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Contents</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown 1">
<a class="dropdown-item" href="#Contents">Contents</a>
</div>
</li>