Hi,

Please add more this code to Customize > Custom CSS to fixed it:

.pencislider-item .penci-image-holder { height: auto !important; }
.pencislider-item .penci-image-holder:before {
    content: '' !important;
    padding-top: 41.66667% !important;
}

Note Important:

1/ You need to use all images on your Penci Slider as the same size. Example: All images has a size 1920x800 px for example. You can use this site to crop/resize your image before upload it to your site.

2/ Change value 41.66667 on the above code to the value you want.

Example: if you want to use images on your slider with the size: 1600 x 700 for example - you need to change value 41.66667 to:

( height / width ) * 100  =  ( 700 / 1600 ) * 100   = 43.75

Hope this help,

Best Regards,

PenciDesign