Adding the following CSS rule to your project HTML fixed the issue:
.row {
margin: 0px !important;
}
However this might cause unwanted behaviour. The suggestion from Bootstrap is to use a container wrapper around row classes, so I modified GetTemplate the following way, which also worked here:
' <div class="container">'+
' <div class="row no-gutters" style="height:100%;">'+
//the rest of the template
' </div>'+
' </div>'+
' <div class="card-footer d-flex flex-nowrap" style="height:'+IntToStr(hPanel)+'px;">'+
//...
'<div class="container"><div class="row" style="height:10px"></div></div>';
It's a matter of figuring out the proper CSS settings.