Hi,
The CSS positioning of the popups on the add to cart comes from your template's CSS:
demo.joomshaper.com/2016/politist/templa...ist/css/template.css
#sbox-window {
top: 50% !important;
left: 50% !important;
transform: translate(-50%,-50%) !important;
height: 200px !important;
width: 500px !important;
}
#sbox-window #sbox-content iframe {
width: 500px !important;
}
If you remove that CSS, it displays fine all the time as far as I can see. I would recommend to contact your template provider to notify them about the situation.