The “click screen” div that’s supposed to block scrolls, but be deleted as soon as you click it, is sticking around longer than it’s wanted.
<div class="maps-onebox">
<!-- this thing -->
<div style="background:transparent;position:relative;width:690px;height:400px;top:400px;margin-top:-400px;"></div>
<iframe src="https://www.google.com/maps/d/embed?mid=za0Bx0koO4sk.kHCbG4TApEP4" width="690" height="400" frameborder="0" style="border:0">&lt;img src="https://www.google.com/maps/d/thumbnail?mid=za0Bx0koO4sk.kHCbG4TApEP4" width="120" height="120"&gt;</iframe>
</div>