Rounded colors visible when fading in Easy Slider

On one page i have an easy slider which i want to have rounded corners – as i don’t have such a slider on another page i ended up just using the first class i found – after i experienced, that i’m having trouble with the egdes as they are visible when fading, i ended messing it up completely and just tried this and that. Here is what i have at the moment (which does not really help anyway):

#av_section_1 > div > main > div > div
{
border-radius: 25px;
border: 2px solid #F8F5EB;
z-index; auto;
}

.post-entry-166
{
border-radius: 25px;
}

.avia-slideshow
{
border-radius: 25px;
}

.avia-fade-slider
{
border-radius: 25px;
}

.active-slide
{
border-radius: 25px;
}

You can see the Problem here:

http://messerausch.aninova.de/enfold-support/rounded-corner-fading-issue-1.png <- this is how i want it
http://messerausch.aninova.de/enfold-support/rounded-corner-fading-issue-2.png <- this is the issue (corners!)

I’d appreciate any help of what i have to add to just address THIS slider and have the corners rounded even when fading or sliding.

Thanks a lot in advance. I’ve created an administration-account so you can see for yourself if necessary, please see details below.

Cheers