Hi there,

Use the following custom css in Salient > General settings > CSS/Script related:

@media only screen and (max-width: 1000px){
    body.page-template.page-template-template-portfolio .container, .post-area.standard-minimal.full-width-content .post .inner-wrap {
    margin: inherit;
}
}

Thanks.

Remove the CSS provided earlier and use below.

Add this into the Custom CSS box located in your Salient Options panel (All custom css provided is tested in the Live Browser so it will work as intended . If you cant see any changes make sure there is no red cross in the Custom CSS Box as that syntax error would cause all css below it to not show up on the Frontend):

@media only screen and (max-width: 690px) {
    body .portfolio-items[data-gutter="15px"][data-col-num="elastic"].fullwidth-constrained, body .portfolio-items[data-gutter="15px"]:not([data-col-num="elastic"]), body .portfolio-items[data-gutter="default"]:not([data-col-num="elastic"]) {
        margin-left: -15px !important;
        margin-top: -15px !important;
    }
}

Thanks