CSS Animation Animation Not Fading Out

I’m a little stumped trying to sort out a simple animation of a background-image fading in and out on hover. Seemingly the web browser says undefined though my keyframes are defined:

  .elementor-section.elementor-element.core-range
     > .elementor-container:hover
     .product-image::before {
     animation: coreRangeBackground 0.3s ease-in-out 0.3s;
     animation-fill-mode: forwards;
  }

  @keyframes coreRangeBackground {
     100% { background-image: url("./images/core-range-bg.svg"); }
  }

  .elementor-section.elementor-element.phases-of-the-moon
     > .elementor-container:hover
     .product-image::before {
     animation-name: phasesMoonBackground;
     animation-duration: 0.3s;
     animation-timing-function: ease-in-out;
     animation-delay: 0.3s;
     animation-fill-mode: forwards;
  }

  @keyframes phasesMoonBackground {
     100% { background-image: url("./images/phases-of-the-moon-bg.svg"); }
  }

EDIT: Can’t animate background images, swapped to opacity

The image fades in with the ease, but after unhover it just instantly flicks to no image instead of easing out.

  .elementor-section.elementor-element.product-card
     > .elementor-container
     .product-image::before {
     transition: all 0.3s ease-in-out;
     position: absolute;
     width: 100%;
     height: 100%;
     background-repeat: no-repeat;
     background-size: cover;
     top: 0;
     left: 0;
     display: block;
     content: "";
  }

  .elementor-section.elementor-element.core-range
     > .elementor-container:hover
     .product-image::before {
     animation: productCardBackgroundHover 0.3s ease-in-out;
     animation-fill-mode: forwards;
     background-image: url("./images/core-range-bg.svg");
  }

  .elementor-section.elementor-element.phases-of-the-moon
     > .elementor-container:hover
     .product-image::before {
     animation: productCardBackgroundHover 0.3s ease-in-out;
     animation-fill-mode: forwards;
     background-image: url("./images/phases-of-the-moon-bg.svg");
  }

  @keyframes productCardBackgroundHover {
     0% { opacity: 0; }
     100% { opacity: 1; }
  }