media grid behavior problem

Visual Composer (which came bundled with Highend, but for which I can find no license key and thus cannot get support from the author) has a “media grid” element for displaying images. The element works OK, but when the images render, they’ve got a shadow overlay that seems to be associated with the forward or backward arrows on either side of the image. The overlay appears only when one hovers over either the left half or right half of the image, and covers either the left half or right half (respectively) depending on which side the cursor’s on. How can I get rid of this annoying overlay?