A problem repeatedly occurred showing on collection page on iPhone/Mobile

[slatsolution]

When ever I click into a product then click back to the collection page and scroll it show this.
i just added this line of code in product card to show metafield

<span class="plank_label {{ card_product.metafields.custom.slat_count_per_plank.value | downcase | replace: ' ', '-'  }}">
  {{card_product.metafields.custom.slat_count_per_plank.value}}
 </span>