css - When using column-count, overflowing content completely disappears in all but first column, why?

Question

When using column-count in a wrapper, and the containers in the wrapper have border-radius applied, and content in the container is overflowing, the content completely disappears in all the columns, except the first one.

Here is my example: https://jsfiddle.net/f4nd7tta/
The red semi-circle is only visible in the first column, why?

#main_wrap{
    width:100%;
    border:solid 1px black;
    -moz-column-count: 3;
    -webkit-column-count: 3;
    column-count: 3;
}
#main_wrap > div{
    border-radius:5px;
    overflow:hidden;
    position:relative;
    -moz-column-break-inside: avoid;
    -webkit-column-break-inside: avoid;
    column-break-inside: avoid;
    width:70%;
    height:300px;
    border:solid 2px grey;
    margin:2px;
}
#main_wrap > div > div{
    position:absolute;
    background:red;
    border-radius:40px;
    width:40px;
    height:40px;
    right:-20px;
    top:0;
}

<div id="main_wrap">
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
    <div><div></div></div>
</div>

Answer 1

I honestly have no idea why this happens, I am looking the docs if they have specified this behavior, I want to check whether its intentional or it's a bug. For now I am using

-webkit-transform: translateX(0);
-moz-transform: translateX(0);
transform: translateX(0);

And it works... So add the above properties in #main_wrap > div and I think if you are ruling out the vendor prefixes than transform: translateX(0); is sufficient.

Demo

Ok, I think it's a bug :

Issue 84030 : CSS 3 Column bug (overflow: hidden like functionality where it shouldn't)

The absolute positioned elements are clipped as if there is an overflow: hidden applied to the box. However, applying overflow: visible or any other rule does not fix the problem

---

I thought more over this, as I suggested the first solution which I randomly inserted the properties and it worked, there is also a way where you can legally do what you are doing by using a clip property and you won't need overflow: hidden; anymore..

#main_wrap > div > div{
    position:absolute;
    background:red;
    border-radius:40px;
    width:40px;
    height:40px;
    right:-20px;
    top:0;
    clip: rect(0px,20px,40px,0px);
}

Demo 2 (Clip Demo)