Internet Explorer: top direction selected, section expanding bottom side

[iboffa]

Hi, I have defined my resizable sectionthis way:

Here there are the involved classes:

.lowthird{
min-height: 225px;
background: #0f1423; /* For browsers that do not support gradients /
background: -webkit-linear-gradient(#0f1423, #364c63); / For Safari 5.1 to 6.0 /
background: -o-linear-gradient(#0f1423, #364c63); / For Opera 11.1 to 12.0 /
background: -moz-linear-gradient(#0f1423, #364c63); / For Firefox 3.6 to 15 /
background: linear-gradient(#0f1423, #364c63); / Standard syntax */
z-index: 999;
left: 0;
right: 0;
bottom: 0;
flex: 1;
display: flex;
flex-flow: row nowrap;
margin-top: 6px;
}

@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {
.lowthird{
bottom: 0;
}
}

.top-border{
border-top-style: solid;
border-top-width: 1px;
border-top-color: #edeeed;
}

In other browsers it works perfectly, but in IE it starts expanding on the bottom side